Can’t recommend specific brands but I will waffle on about fit.
Getting the right sized frame is very important with road bikes, arguably more so than MTBs where you don’t spend the same amount of time in one position.
IMO the horizontal top tube length (or equiv if it’s a sloping top tube) takes precedence over the seat tube length so I’d definitely recommend sitting on a couple of different sized bikes if you’re not sure of sizing.
I’m 5′ 10″ with a slightly short torso and a recent bike fit recommended a 547mm top tube. – I typically ride a 54cm frame and make any adjustments with stem lengths.
Things like 12cm+ stems and 3cm+ of h/s spacers are indicators of the wrong size frame.
I’d personally not bother with flat bars as drops will give you more hand positions.
Similarly unless you live in a really hilly area, you won’t need a triple chainset. A 34/50 compact c set + 12/25 cassette should get you up just about any hill.
Oh and you don’t need disk brakes on a road bike either.