Welcome to carrying.
You will find that, in general, holsters are like shoes. Fit, comfort, style, price, etc., all play a unique and personal part in selecting a holster that works for you. There are, however, a few objective criteria you should consider. I encourage you to watch John Corriea's Active Self Protection video in which he describes his "Three Critical Qualities of a Decent Holster."
https://www.youtube.com/watch?v=Ox7GrdjqRXk
In my experience, an outside the waistband (OWB) holster is more comfortable, easier to move on the belt while wearing, easier to draw from. Inside the waistband (IWB) seem to conceal more easily.
Unless your pants are already loose, you will probably want at least one size larger for IWB carry. Of course, the size and shape of the pistol/holster combination will affect the fit.
My 21 year old son is 5' 10", 130lbs. He easily conceals his S&W M&P M2.0 Compact 9mm 4" (double stack 15+1) in a Bravo Concealment DOS without changing pants size. My younger brother is older and heavier than my son. He had to go a size larger to comfortably carry his S&W M&P M2.0 Shield 9mm (single stack 8+1) in a Raven Concealment holster.
My wife has a Comp-Tac International OWB holster for her Walther PPS M2 LE (single stack 89, but prefers to carry her pistol in her front pocket in a Remora RFT pocket holster. My 86 year old father carries his S&W M&P M2.0 Compact 9mm 4inch in an OWB Safariland 7TS ALS retention holster with a belt clip. He usually wears a jacket when outside the house.
Previously, at 5' 10" 186lbs, I carried my Tanfoglio BTA90 in a Gaclo King-Tuk IWB hybrid holster and concealed it with a tucked-in shirt. Now I carry my S&W M&P M2.0 9mm 5inch in an OWB Safariland 7TS ALS (double stack 17+1) with Guard and QLS. I incidentally conceal as the weather dictates or when wearing a suit.
Age, body type, personal preference, etc., vary from person to person and make comparisons difficult.KR Training, where I've done most of my pistol training, has a large selection of holsters and plastic pistols such that customers can try various combinations. I was able to try a Safariland ALS holster with my M&P before I bought an ALS holster for myself. Perhaps a local trainer/reseller can help you out in trying things on.