I'm not sure high-speed cards are critical for single images . . .
It absolutely shouldn't matter.
The difference would generally only come into play if you program your cam for a very short delay between triggering events, i.e. 1 second, 5 seconds, 10 seconds, etc. But if you're using like 1 minute or longer delay, shouldn't matter much what the card speed. You might miss some subsequent triggering pics with a slow card, but that shouldn't cause the cam not to work, after it's had time to "recover" (should be less than a minute typically).
I shoot only HD or higher-quality video, and I won't use a card under 100mb/s transfer rate. Prefer at least 120mb/s.
Same.
I'm generally only using 120mb/s or higher with all my cell cams, regardless of brand.
About all the new SD cards I'm buying are 64gb or greater capacity with 140mb/s transfer speeds.
Unfortunately, these will not work in my Tactacams (which only take up to a 32gb card).
Most of my cell cams are Brownings, which accept up to a 512 gb card. If I use them on video mode, I typically use a 128gb card, as you can fill up a 32 gb card pretty fast in video mode, negating part of why I'm using cell cams (which is to have no need to go replace the sd card).
It can be frustrating to have your SD card fill up when your batteries don't need changing.