How do plugins affect the site?

Question

WordPress

Hello.
I want to clarify for myself how plugins and their number affect the work of the site on WordPress. Please share your opinion based on experience or technical nuances. I looked at various information on the Internet, most of the articles were written a long time ago and could lose their relevance, and a recent conversation with one VP specialist brought even more doubts.
What is the best way to implement additional functionality: through a plugin (using a ready-made or by writing / ordering it) or simply by making changes to existing files?
How bad is it to use a fancy plugin for a feature or two? For example, Jetpack has a lot of functionality, but only a third of the functions are used. Would it be better to use several plugins of the required functionality, or is it better to install such a “combine” that does not work at full capacity?
Are there any recommendations for limiting the number of plugins? For example, no more than 10-20-30.
For convenience, let's consider the situation when the plugin is written competently, and not by a person with low qualifications. It is clear that you can write through one place.
UPD Let there be a case when the VI is used for its intended purpose, and not for one page or a very complex and cumbersome system. There are a lot of special cases and it is impossible to cover them all. It is important for me to understand the essence, and projecting onto a specific project scale for comparison is a second matter.
In general, I will be glad to hear an opinion not only on the voiced examples, but also on plugins in general.

Answer 1

https://wordpress.org/plugins/p3-profiler/
Show which plugins are slowing down the site.

Answer 2

It all depends on each specific project and the server on which it will be running. Well, the task must be clearly understood.
Take, for example, some simple landing page that is not updated often. And let's say that you have a task - to enter all sorts of SEO things like keywords, meta, all sorts there, og: title, and so on. Putting Yoast SEO for this, which is essentially a comprehensive SEO solution for WordPress, for the sake of just one page, is not the best solution for a weak server. You can put this plugin on the dev-server, fill in all the SEO in it, then look at the generated code, copy it directly into the template. After that, the plugin can already be deleted - you will get a dozen or two fewer requests to the database. Well, it's the same with other plugins. But specifically, this action is logical to apply only on the landing page, which will change once a month maximum. Otherwise, each time editing the SEO through the code is an extra waste of time, it’s easier to install the plugin.
But this is all, again, specifically for this task.
" How bad is it to use a fancy plugin for one or two functions? For example, Jetpack has a lot of functionality, but only a third of the functions are used. Is it better to use several plugins of the desired functionality or is it better to install such a "combine" that does not work at full capacity? "- here you need to estimate the amount of work to implement the desired functions in your template without using a plugin. If it’s really faster and easier to install a plugin and at the same time technical resources allow you not to worry about the number of plugins, it’s easier to install a plugin (in terms of man-hours spent, which need to be converted into a monetary equivalent). Moreover, the Jetpack is a proven thing.
Are there any recommendations for limiting the number of plugins? For example, no more than 10-20-30. - it is impossible to say exactly. Depends solely on the capabilities of your server.
Another moment with the number - see that after 20 plugins your admin panel does not overgrow with hundreds of buttons that will not even fit on the screen at a time. I solve this moment by installing a custom admin panel style for non-superadmins, in which I hide absolutely all unnecessary buttons, leaving only what is safe for an inexperienced user and relates specifically to the daily tasks of the developed site.

Answer 3

For small projects, it doesn't matter. For large ones, WordPress is strange to use.

Answer 4

How best to implement additional functionality

Only through the plugin, you can manually change the theme files - functions.php and templates. If the functionality is small, you can write it in functions.php.
The structure of WP is like a tree, where each branch is a filter or an action. Plugins just add a reference to the method\function to the list of actions for each branch that the engine will need to perform. The plugin itself, therefore, does not affect performance - it all depends on exactly what functions WP will need to perform. On average, if you have about 50 medium-sized plugins, there is nothing to worry about - most likely, you will not even notice a slowdown in performance. 20-30 plug-ins and less about nothing at all, as it flew, it will continue to fly. Plus, you can install a caching plugin to speed up your work, or even switch to php7 and speed up WP by 2 times. On one corporate site (~30 plug-ins with a very wide functionality + self-writing), this is done, it opens almost instantly.
Of course, a lot depends on the plugin itself and how crookedly it is written - I constantly meet both a refusal to follow the recommendations in the dev guide, and just hellish code that you won’t look at without tears (although it’s possible that it’s fast in terms of performance). But this is what WP is good for: if any plugin affects the system too much, you can almost always find a better one.
Summing up, in general, you can set as much as you need, although solely for the beauty and purity of the site's ecosystem, to prevent possible collisions and bugs due to incompatibility, I prefer to do with the possible minimum.

Answer 5

More plugins -> more potential holes and problems.
Divide and rule.
About separation, the view of a person on the software itself is already in effect. I follow do one thing, and do it well , within the bounds of common sense, of course.

Answer 6

Differently.
To make it clearer, imagine that you have a file with a thousand lines of code.
You can include this file as one big plugin,
or split this code into a thousand small plugins one line at a time and include this code as a thousand plugins,
or include this code in your theme's functions.php file.
If the code is of good quality, there will be no difference.
The number of plugins does not directly affect the operation of the site. It affects the quality of the code.
Some plugins may not be compatible with each other.
Or some of the plugins could be written by an attacker and he could access the site through such a plugin.
Or one of the developers made a mistake when writing a plugin, because of which the site slows down.
The more plugins you have written by different people, the greater the chance for one of these problems to appear.