I have narrowed my 22 suppressor host down to a Ruger Tactical (steel frame) or a Silencer Shop Ruger with the 2" barrel. From prior reading, some say the 2" barrel over a 4+" has a noticeable sound suppression difference using standard velocity ammo. How much of a difference should I truly expect to hear from the two different barrel lengths? My main goal is sound suppression for this setup.

If you keep it at 4.5" the difference is 0. Your not going to hear a difference.
4.5" and below will keep most rimfire ammo under 1300fps subsonic regardless of the host weapon. I have a mkiv tactical, 10/22 and ar22 all with 4.5" barrels and they keep all 1300fps ammo subsonic.
5"+ is when you have rimfire ammo going supersonic.

The smaller barrel is to keep it smaller, and I think a big factor is that it looks cool.
I've owned and shot both 2" and 4.5" barreled .22lrs.

I stick with 4.5" barrels. I've also had better reliability with 4.5" barrels and slightly better accuracy.

Also, the mounting holes for optics are different on the silencer shop mark iv than standard mark iv pistols so you will need a silencer shop specific mount for it if you are mounting an optic which i am assuming you are, so that could be a decision factor for you as well.

All things being equal the shorter the barrel ( un suppressed) the louder it is. I am not sold on red dots, so my pistol better have a decent set of sights. The silencer shop snub doesn’t so a deal breaker for me.

The vast majority of HIGH velocity ammo is still subsonic in a 4.5”, and nearly all standard velocity will be as well. I use standard velocity ( aka subsonic) match ammo when using a can.
I don’t care for cheap bulk domestic ammo, and think if you invest in a supressor host and can, should use a good quality ammo in it.

I splurged and found a MK IZ Tactical today and snagged it. Shooting subs is less sound than my 10/22 too! Glad I went this route to have further choices with it rather than the SS 2"

Just a note-

For many years, standard velocity ammo didn’t sell nearly as well in the American market as high velocity, with standard used pretty much only by competitive match shooters. When supressors became popular, the ammo companies saw an opportunity. Let’s take that same standard velocity ammo that wasn’t selling that well, put it in a box labeled “subsonic” or “supressor” and charge more for it! They did and a lot of consumers gobbled it up.
Point is while there are some loads slightly different designed for suppression use, most of the ammo is just plain old standard velocity ammo.
I am something of a 22 ammo snob from my competition background, so prefer a standard velocity match ammo most of the time and again almost all standard velocity match/ target ammo is subsonic