How much distance do you require to stop? This seems like a simple question but its not. It varies widely from one person to the next. You never want your stop distance to exceed the range of visibility and in the case of night rides the throw of your illumination.
What kinds of terrain are you riding over? A city commute can be just as bumpy / jarring as anything off-pavement.
Is your preference a frame mount or a bar mount? Do you want a fixed aim headlight like a car? or do you want to aim light like a motorbike?
For a while I used a mount like this. It wasn’t stable enough for my liking. Although I never had a problem with it actually dropping the light on my smooth paved commutes and pack gravel trails. My daughter uses it now for her school commute. She likes it because the light can easily be removed.
I have been using this generic Amazon mount and have no major complaints other than the orange color. I haven’t had any issues with it, but note my light is really small and not heavy at all.
I really like the Lumintop B01 but it really doesn’t have a high mode. The medium is too low unless you ride exclusively in rural areas with no traffic, so high is the default and turbo is pretty useless because it’s on a short timer. Still a great light for $35 just not bright enough for the urban areas I sometimes ride in.
Right now I use a Convoy S2+ SST40, it has a perfect beam for my riding style as well as good brightness and runtime.
Two-fish lockblocks or knockoffs work great and are cheap. I use them exclusively on all my bikes, including MTB and haven’t had any issues. No reason not to use your Q8 IMO.
I have a both and is nice combo. But to fit EC01 in Fenix holder is good to remove supplied thick rubbers. In that case you have more space for screws. I replaced them with thin rubber from inner bycicle tube. I think to try and buy EC03 because it have same battery tube as EC01 and I want to use it wtih Fenix holder.