The main use will be low voltage low current electronics: embedded systems, MCU boards, I2C/SPI connections... things with voltages under 5V and currents under 500mA. What a want basically is to measure the values with good precision and reliability.
You can easily use (eg.) an Arduino for logging low voltage DC. It can do multiple channels, too, and high speed if needed. Handheld meters will only send a couple of values per second.
As for the meter: Go with the UT139C that you know or get some Anengs. These are good:
https://es.aliexpress.com/item/33004463675.htmlReliability? There are exceptions but I think it's more productive to have lots of meters around to cross-check weird readings than to aim for a perfect meter.
Whatever meter(s) you go for, budget enough to get some nice gold-plated test leads to go with them. They
do make a difference and they don't have to be expensive, eg. these are
much better than the leads that came with my Aneng:
https://www.aliexpress.com/item/33006553337.htmlFor less common occasions I might need to measure mains AC one in a while, but not that important.
For occasional use you'll be safe with the meters above.
Correct procedure is at least as important as the meter (check three times that the leads are in the right holes and the selector switch is in the right place, wear a glove, don't do anything risky without somebody else around to notice if you scream and fall over, that sort of thing...)
Do all these meters have to be identical? Get a cheap Brymen or Fluke 101 to complement the others.