Hi Jaybee & welcome. Those two bikes you mentioned are a good place to start. Regarding the "big adjustment" some of it might be physical so ensuring that the bike fits you really well is paramount. Stand over is important, but I would venture to say that reach is even more important. I think the other part is "mental" -meaning that if you think it's gonna be a big deal then it probably will.
Do you have local bike shops where you can test ride these bikes in different sizes? Can you tell us how you came to choose those two bikes? That will help us figure out how to best provide the type of info. you're looking for.
There is a woman on this forum who just bought a Surly Pacer yesterday and I hope she will tell you something helpful.
I had not been on a road bike for 27 years, had the "wrong" bikes off & on for about 15 years, then in October bought a Trek Hybrid. I have already grown out of it and just bought a Surly Cross Check in Robin's Egg Blue. It's technically a cyclocross bike, but around here it gets built up for all sorts of riding. For me it's my all around bike. It didn't take me long to get used to different handlebars and the bar end shifters. So just make the decision to do it, then do it. You'll be fine.
Happy riding.