It depends on what you want to do. If you want to use the Nvme SSD's as read/write cache you can use any of them. If you want to make a volume with the Nvme SSD, Synology requires their own. You cannot create volumes with non Synology Nvme SSD's.

In my DS1821+ I have used 2 Samsung 970 Pro as SSD cache group and they work without any problems on the part of Samsung and Synology.
The exact type: Samsung 970 PRO MZ-V7P512BW SSD 512 GB