Some of these are subjective to the user. Personally there are a few I haven't done. Preload is definitely something I'm going to look into doing. I do use the 'nightlite'. Bleachbit however, is something that I won't. That's your call. Have heard many users complain it has damaged their systems. I use 'Stacer'. Chose Brave Browser over Chrome. I also use Firefox, but have never made the changes in video so can't speak to that. Change DNS sounds interesting, will check that out. Ubuntu Restricted Extra, I have done and would recommend. Same goes for Timeshift, which I store onto an external drive in case of hard drive failure or if it gets corrupted to bad. As for the others mentioned, I believe they are all safe to try. Hopefully others in the forum will give you their opinions as well.