Queries on brakes for drop bar fun

I may well be overthinking this.

Mentally casting my eyes over a few bikes that may replace my current gravel bike. Not liking the price or spec of full builds so considering frame and going from there, but stuck on what probably is straightforward to answer in that the two frames I like have IS mounts for brakes on frame and forks.

I like my current shimano grx so am trying to work out how to get similar hydro and gravel / mtb friendly brakes which are designed for flat mount to play nicely with the IS mounts. I can’t see any adapters like you get for IS to PM?

Or am I stuck with cable brifters and callipers? Or some weird half and half job where I’d be buying callipers and brifters separate? Or am I being dumb?

I have used some fairly cheap Aliexpress/Ebay IS-Flat adapters in the past, and they have worked fine.

https://www.ebay.co.uk/itm/395249529552?var=663840138246&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338365712&toolid=20006&customid=EB247307452&

Look a bit dodgy (Not the same listing I got mine from, but the same design)
Everything worked fine once set up, and you wouldn’t know they’d been bodged.