Got a PS5 slim and looking forward get a SSD to increase storage.
Any recommendations? 1tb or 2tb ??
Depends entirely how you manage your games and your internet speed.
If you play one game at a time, the bog standard drive on the console will do ok.
If you play multiple games or don't have the capacity to keep downloading games/patches, get the highest possible.
I bought a 4TB NVME when I got my Samsung phone, it set me back £150 as I got a decent deal on it, but it does mean I can put all my PS5 games on it, so they're readily available.
The other alternative is to look at an 8TB Samsung Evo and just be done with it, can stick all your PS4 and PS5 games on one drive then.