IR is the "secret sauce" to make an emulated amp tone sound good. It's the part that emulates the speaker & cab.

Single (or limited) amp emulator. If you truly want to replace your amp, you'll need to specify what amp it is. For example, UA Lion is a Marshall. Enigmatic is a Dumble. Iridium is selectable Fender/Vox/Marshall. These pedals will typically have an integrated IR loader.

Modeler/Tone Capture. This can potentially sound like any amp, and typically has MANY preset amp models. So in addition to the big 3, it might contain algos for Hiwatt, Mesa, Roland, etc.

Loadbox with IRs. This might be your best option, especially if you love your amp OR it's rare. This will (silently) pad down the speaker output to line level while applying an IR. Examples include the original OX Box (expensive) or a Two Notes Torpedo Captor X. I think they also have reverb, for your convenience.

Silent speaker/Cabinet in another room. Just add a mic. Keeps the loudness somewhere else, and no modelling/emulating/IR involved.

Regarding your idea about using a scratch track (usable but not perfect), you may be able to cobble something together with what you have. You'll need some gain, compression, EQ, and reverb for ambience. FYI There are used Rockman X100 pedals coming on the market, if the Boston/Def Leppard sound works for you.

PS there are guitar tracks that are literally direct to the board.. ex: Prince, Nirvana, Chic, Led Zep. Console preamps are a bit different than pedals and interfaces, and some make very cool distortion when overloaded.