Word of warning, I did one of these about 3 years ago, and it left me in a tremendous deal of pain and a journey that reminded me heavily of OPs post.
After years I am finally doing mostly better, but would not wish that on anyone. Unfortunately I'm not an expert and can't tell you what is better, but there are few decisions I regret more than doing a cheap over the counter nightguard.
Once you use something like [1] where they make a custom one you'll never want to use the supermarket variety again. I would grind my way through the supermarket kind every 2-3 months but this one has held up really well and it cleans easily with denture cleaning solutions.
I tried all kinds of cheap options before shelling out the big bucks for a custom made guard. It's a night and day difference. The custom guards are ridiculously priced, but I cannot go back to OTC guards after having one.
The ones you are recommending in your comment history were not much cheaper than my custom, 3-D printed one from my dentist. Impression molded guards have nothing on what I ended up getting. I wish I knew the name of the device that was used to make it.