I don’t think holding tight onto the drops is a good idea. That’s an excellent way to skin your knuckles to the bone. I’ve seen it. Doesn’t heal well. Still wondering why no road gloves have any knuckle protection.

Holding onto the tops is better, but if you have the time/awareness to switch to your tops, you probably have the time to mitigate the crash.

I’ve heard that the best thing is to cross your arms across your chest and fall on your back. Biggest surface area, and your spine is really good at dissipating impacts in that direction.

Screw that up, though, and you could be looking at a fractured vertebra and possible spinal cord damage?

It’s hard to say “this is the best way to crash”. Most of the time, if you’re going down, it’s because you didn’t anticipate whatever caused you to go down. Going down is gonna hurt all the time, and sometimes you get unlucky and you fall just the wrong way to really mess yourself up.

I prefer to do my PT in advance. If your body is in shambles and then you get hurt, it’s gonna be a lot harder to get back to normal. I had a friend who did a lot of lifting get absolutely destroyed by an SUV while commuting on the bike (not a recreational cyclist). Tons of shattered bones, ripped tendons etc. He made what I consider to be a miraculous recovery, and barring the nerves that were destroyed beyond repair, has made a nearly complete comeback and is back in the gym, pumping iron. Not saying that’s evidence, but it’s an example. Being a stronger person means being more resilient during impact and having an easier time recovering.

It also helps to ride defensively. Perhaps even paranoid-ly. Yes, you’ll always be slower that way. But if it means you get to ride more, you’ll come out stronger in the long run. So many of my teammates have crashed hard when they were feeling amazing on the bike, only to have to claw back all that fitness. We don’t get paid to do this, and it’s only your ego that takes the hit if you tap those brakes once in a while.

EDIT: Sorry for the off topic rambling. Just feel strongly about this subject

double edit: I read over your crash scenarios again. Both of them seem extremely avoidable considering that they’re both solo and not really related to equipment failure (unless you mean your handlebars broke). For #1: are you using clipless pedals? Roadies like those because they’re very secure and don’t slip in the rain. I’ve had flat (metal) pedals like that and they are no good. I’d recommend something with more aggressive bite if you insist on flat pedals.
For #2: hindsight is 20/20 but hitting a pothole should pretty much never be a crash unless it brings you to a dead stop (in which case you should see it coming). A lot of people like to drape their hands loosely over the hoods but this is not a secure position. My friend did this on a 30mph descent and lost his grip when he hit a rock. Unless you are absolutely sure there is no immediate threat ahead of you (like on climbs), you should maintain a secure grip on the bars.