Which RAM to choose for imac 2020 27? And will there be a guarantee left when adding?

Question

RAM

Hello. Not so long ago I took an imac 27 2020, with 8 GB of RAM. I want to expand it, because the procedure is quite simple, and therefore there are a number of questions:
1) Will I still have a guarantee with self-expansion?
2) Watching the tutorials, how everyone expands - everyone takes 2 memory sticks, is it necessary or can I take, for example, one for 16 and not worry?
3) can someone advise specific models of RAM?
Thanks in advance for your replies

Answer 1

1. will remain.
2. take two for multi-channel work. one will work too.
3. I always take owc, crucial or hynix.
specific ones can be peeped, for example, on amazon