May seem obvious, but make sure you get an electrical outlet put in near the toilet. I have a bidet seat and I had to run a line to mine in my 1950’s ranch.
I have a TOTO bidet seat and like it a lot, but it sounds like you’re looking for a toilet/bidet that is one unit. Probably still relevant is to think about cleaning. My seat come off very easy for cleaning. Not sure how a built in will work, but cleaning is still a consideration.
Also, if the bidet is part of the toilet, make sure it’s a solid company. An add on seat can be replaced. A built in will need a part sooner or later and you don’t want to have to get a new toilet because the part is not available.