iMovie is (was?) quite capable and inexpensive, and I believe there are reasonably priced versions of Final Cut Express as well on that platform. When I last used an (old) mac you could get Final Cut Express for around fifty dollars, and a copy of Motion for the same, which is kind of like having after effects and premier.
It depends. If your videos are already processed for editing then it’s not significantly harder than doing the same cut and splice jobs in Final Cut or Premier. It’s not as tolerant of splicing random clips as ex. iMovie and friends are, but professional VSEs and compositing software are built around workflows where the camera footage has been pre-processed for editing as well.