I've tried the sleeves, but they are bulky, and it is difficult to see if a good connection is made.
I've also tried manual soldering but it is always difficult to align the wires with grippers, and the temperature causes the grippers to go through the insulation. And you need shrink tubing.
However, as a pictoral reference the newer documents arent as clear for me, so this online database is still very useful.
If it's just low volt, low current, low mechanical stress stuff indoors - just twist and solder and wrap a bit of elec tape around it. But if it matters, break out the crimp tool.
From what I have read high current connections shouldn't be soldered (heat may melt solder) so you crimp not solder.
Far less bulky than they appear because they shrink while being heated so they're barely thicker than the wire. They can also be bent while hot which lets you get joints into tiny places.
So far, haven't had a single one fail, although I'm still dubious at using them on corroded or non-copper wires.
Alternatively, use self-vulcanizing silicone tape instead of heat shrink. That stuff doesn't need to be put on first, and doesn't need a heat gun, but is harder to apply on small wires due to the need to stretch it as it's applied.
Don't use the shitty metal alligator grippers you get on "helping hands", they're terrible even when not heating the wire much. A small smooth-jawed vice or two is far better for small work, e.g. a PanaVise model 201.
Eg https://www.toolstation.com/ideal-industries-in-line-push-in...