I have a Hero 4 Silver.
I bought it about 2 years ago when the only other "better" one what the Hero 4 Black.
I like it and the kids really get a kick out of it also.
I have purchased the majority of my accessories, both GoPro and others, from B & H Photo.
https://www.bhphotovideo.com/ Their prices are good and being able to search and compare with their website is helpful. The 3rd party mounts are really well made also.
The 1 GoPro branded mount that I really like is the one with a swivel ball. So much easier to maneuver.
https://www.bhphotovideo.com/c/product/1186634-REG/gopro_abjqr_001_ball_joint_buckle.html
I think having a screen on the back is a good idea and helps lining up shots. My regular video camera has a screen and my DSLR does not have any active screen which bugs me. So for the GoPro I found it useful to pay for the screen.
I also have a Remote with a screen which is really good. The only thing that doesn't work is the WiFi connection does not work through water but once out of water the connection is made again. The original remote that I had, used the GoPro LCD backpack but is no longer made. I broke it when I left the charging port opened and water got in it. The company actually replaced it with their new remote so I have not had a chance to use it in the water yet. But it works well the limited time I tried it.
https://www.removu.com/
I like photography but I am not a professional. So to me the image quality is amazing given the size and what the camera is used for. The sound even records well even while in the water proof case.
I have toyed with the idea upgrading to the new 5. Whether I sell the other one or not is still undecided. If I were to sell there are some accessories (small amount) that will not work with the 5 that I would need to sell also since they are not compatible. Another thing to consider when planing your purchase(s).