First of all welcome to the forum. I think that most of what you plan to do sounds good to me. The only changes I would suggest is going to a range with rentals and trying various models. I find there can be a big difference between how a gun feels in the store and how it feels when you shoot it. Especially when it comes to smaller carry guns. I also think that caliber makes a big difference. You are running into the age old problem. Full size handguns shoot great but are heavy. Small light carry guns are much easier to carry and conceal but have much more felt recoil so they are not so much fun to practice with.
Semi auto pistols are great if you have taken the time to practice. But if you don't take the time, operation can be problematic. I for one do not want any problems if I was going to defend myself or family. I would highly recommend that you decide on a method of operation stick to that method. I have invested in different handguns for different purposes. I have a HK Mark 23 that I use in three gun matches. But for defense I use Glock handguns. I have a Glock 30 (mid size .45) for carry and a Glock 21 (full size .45) for the house. I have practiced with them a lot. I like that there isn't the extra step of of manipulating an external safety.
Training is great. I would highly recommend it. But mental preparedness is just as important. When to pull out a gun is as important than how you get to and pull out a gun. Are you prepared for the fall out of actually defending yourself or a loved one? Shooting an aggressive wild animal would be easier for me than shooting an aggressive person. What does the law where you live say about defending yourself? What is allowed is different in different states. To me most of the accessories question come down to your personal preferences. Some want as absolutely cheap as they can find it. Others must have the finest leather. What is your priority? Good luck with your defensive handgun project.