Does a meter that has more feature is not as accurate as a meter with less feature?
I'm not any kind of expert when it comes to meters, but they usually have an accuracy table in the product description or documentation, and while it may be the case that some models with more features might be less accurate than some other with less features, I don't think that this is a general rule, especially since (usually) meters with more features are more expensive, at least from the same brand (although specially rugged, safer meters might have less features and be more expensive). So, being more expensive, they may have some space to get more accuracy as well.
There is another parameter, called counts, which describes what can be displayed on the screen (e.g. 2000 counts, 4000 counts, 6000 counts, 9000 counts, and so on) but this is not the same as accuracy.
Let's take some meter as an example (I know nothing about this specific meter):
"True RMS Digital Multimeters UT139C"
http://www.uni-trend.com/productsdetail_1147_901_901.htmlUnder "Technical Specifications" you can check the meter accuracy, for example:
DC Voltage (V) 60mV/600mV/6V/60V/600V ±(0.5%+2)
Where the +- (0.5% + 2) is saying how inaccurate the reading can be.
If we look at a different meter and the same range, AN8001 (I guess about $12-15 range), we get this info:
DC voltage: 600mV (+ 1.0%+10), 6V/60V/600V/1000V (+ 0.5%+3)
So, at that range, the UNI-T should be more accurate. There are a lot of other ranges (it's a table, you can check it on the link), so this by itself, just one range, doesn't mean the meter is more accurate overall. Comparing all ranges would tell you a clearer story.
So, to check accuracy of specific meters, you can compare the accuracy data specified. It's worth noting that accuracy has
nothing to do with safety, and some meters can be less safe for general use than others. People will generally recommend safer meters, even if they have less features and less accuracy for the same price, to beginners or any commercial work. Also there are some safety precautions, such as always using the correct range. E.g. if measuring voltage, select voltage and hook the probes in the right position on the multimeter (it's usually written/marked on the multimeter). I'm sure there are a lot of videos out there that explain what, why, and how (I'm just a newbie), as the proper use of a meter (any meter) will definitely be safer than just using it on random ranges, probe positions, and poking random stuff with the probes (including high voltage).