Anything you do with concentration will improve your playing strength. But doing just one thing (openings, endgames, mates-in-2, tactics, watching videos) will only take you so far. However, a combination of all of these, concentrating on your weaknesses, will take you much further. That said, Polgar's book "Chess: 5,334 Problems, Combinations, and Games" is almost entirely mate problems. It doesn't appear to have hurt the Polgar sisters.
Will practising mates in two and three help me improve?
There are those types of mates in twos and threes, but forced in every single line. Those puzzles train not just mere checkmates, but some calculations as well.


A guest on the wonderful Perpetual Chess Podcast put it this way recently: The best way to use puzzles isn't really to improve painstaking, laborious calculation. It's to train your pattern recognition so that you do not have to calculate.
Think of learning to read English. First, kids learn the alphabet and how to recognize letters. Then they learn how to sound out words. Great! They can now read many things. But, true reading proficiency comes later, when through extreme repetition, the reader starts to visually recognize entire words at once.
What this podcast guest suggested was to focus most of your puzzle time on puzzles you've already seen, on the principle that it's better to have a handful of patterns completely nailed than to constantly stare at new ones and have to puzzle them out, then never see them again.

there are specific patterns and techniques with many of the checkmates that were really difficult to try and “figure out” on the fly
studying checkmate patterns really started getting me more aware of squares rather than pieces too
i spent some time drilling the basic/foundational tactical motifs and this has (and continues) to pay off but i would find myself in games with all the tactical alarm bells going off regarding opponent’s king vulnerability and not being able to follow through
learning, drilling, and implementing the patterns of checkmates really filled in a gap in overall tactical pattern awareness
As the title states; will doing a lot of mates in two and mates in three improve my playing strength?I know I should practice all tactics, but is it OK to do only mates for a while? What exactly does it help with? I'm asking because I rather enjoy doing mates in two and three, and if it is beneficial to my progress, I'd like to keep doing them exclusively for a while, until they are easy for me. (Mates in three are presently very hard for me.)