No there isn’t any drawbacks to a sloped top tube other than making the triangle a little smaller. That’s not much of an issue since there are few triangle bags that are going to fit that triangle anyway without going to a custom made unit. The advantage is that you have more standover which you are going to need.

If you have a co-op near you, you can get help with changing parts as well as get cheaper used parts. The Sirrus that I show is using mostly parts from the early 2000s.

As to bikes to look for, look for a Specialized Vita or Trek FX or any number of more modern hybrid bikes. If you don’t want to do the conversion to a drop bar, there are any number of flat bars that offer more hand positions like these or these or something similar. You can find something similar to the Moloko bars at Uncle Ali’s or you could just mount bar ends inboard on the handlebars to get the same effect.

This is a repainted Vita that we no longer have…the Sirrus was a better bike for her because of the discs which allow for a smaller wheel and the Sirrus XXS is just a tad smaller. The bike was a pretty good bike over all, however and worth looking for in used bikes. The hybrids have pretty tire clearance and are, essentially, touring bikes with flat bars or gravel bikes in drag.