Jumping from 170 to 190 cranks is a huge change. Longer cranks do slow your cadence a bit, if you are a spinner from 30 years of using 170mm cranks then jumping to 190 cranks might not agree with your pedaling style without re-training your physiology and technique. At minimum, you should try riding 190 cranks on an existing bike, make sure that you really want to use them before commisioning a frame desiged around them. For most anything except touring/commuting, 190 cranks will require a higher bottom bracket so that you can still pedal through corners on a road bike and/or avoid off-road pedal strikes if this is a MTB or CX bike.
I have very close to your same inseam. I have tried 170, 175 and 180mm cranks for road, MTB and CX over the years. I think that 175 are a good compromize length for my physiology and technique. I could probably go longer for MTB (typically slower cadence) but I like the idea of having all my bikes with same crank length so there is not to much of a physiology change needed when switching between bikes.