Questions about SanDisk Ultra A1

Works without any problems. As far as I know, there were only limitations with the previous versions of the Surface 5 and 6.

Was not there

It has been shown in various tests that SanDisk Ultra can deliver the necessary performance. e.g. https://www.rockpapershotgun.com/best-microsd-cards-for-steam-deck

Yes, I first used it with a Samsung Galaxy S7. Had no problems.

I researched in advance whether you can use the Sandisk Ultra A1 Micro SDXC 512 GB in the Nintendo Switch and it is definitely compatible with the Switch. Whether the size of (512 GB) is necessary or not is up to you. So in short: Yes, you can use it with the Nintendo Switch.

Yes, sure. The card is exfat formatted. On the Mac you can use it that way, or you can reformat it to an Apple format. As you like....