Protip 1 is half-true. A camped present spawn will never respawn. In testing this entire protip, I opened a present and cleared the spawns, then moved to the next closest present still in visual range and did the same. In a little over half an hour of testing various things at present spawn 1, I immediately retreated to the area near present spawn 2, never leaving it for even a full minute. That present at present spawn 2 never respawned the entire time. It might after a certain amount of time, but it is obviously quite long before a forced respawn with somebody right near the spawn point will happen. However, the rest of this protip is untrue. Cleaning the spawns up does not make the present respawn any faster. I sat there with my phone opened to time.gov and the ones that I cleaned up actually took a bit longer for the present to respawn, on average, than the ones where I left the snowies there. There was some variabkility to it, which leads me to believe that the server does a periodic check to see if there's a present there, and then spawns a new one if there isn't, no matter if there are snowies present or not. The longest times were all with cleared snowie spawns, though. This belief that they respawn faster refused to die while the game was live, and it apparently sticks on stubbornly since its resurrection. No matter what, no present took longer than approximately 5 minutes (+/- 10 seconds) to respawn. A good route being necessary to avoid the no-respawn problem of the first part of this protip, you should have very little problem with present respawns if your route is about 10 presents long in circuit, given the general spacing of the presents. Since the snowies tend to be level appropriate to the neighborhood in which the present is opened, and are probably among the most highly-visible critters in the game, I would say that the choice is yours whether you clean them up or not. That is, of course, if you're opening them solo. Don't leave spawns of 5 or more that might include bosses loitering around in a city zone like Atlas Park, just out of common courtesy.
Protip 2 was the only way to get a Winter Lord to spawn for a few years, but was changed later on. I believe that a large team opening presents will still spawn a Winter Lord occasionally, but there is a definite "safeguard" function now, where a Winter Lord will spawn no matter what when a certain number of presents are opened within the zone. That number is pretty high, though, definitely over 50, since I opened my last 50 for Toy Collector without spawning a Winter Lord in the zone, and there wasn't one up anywhere that I could see.