Welcome to the community @Sdnewbie
There are a few places around like GuitarPatches and Toneshare.
But I would encourage you, rather than blindly downloading and using patches which claim to make you sound like Muddy Waters or Duane Allman, learn how to dial in the tone you want into your amp yourself. The first part of this is understanding what sort of tone you are looking for.
And before you say “I told you: southern rock, classic blues, etc.” that’s not really the right answer. Each of these genres has a wide range of tones used by different artists and may artists will have more than one tone they use. Plus a given tone is often applicable to other genres, so labelling them can be unhelpful.
The right answer IMO is critical listening to music with tones you want to replicate, and then trying to understand what characteristics those tones have, which then leads to how to dial them into the amp.
Note that, whilst amps like the THR series have a fair amount of bells and whistles in terms of effects and effect options, you can generally ignore these and focus on the core amp tone which is basically: amp model, gain, and EQ.
A few important things to be aware of:
- If you go the patch download route, the patches on most websites are often not that great, which is why you will often find dozens of different takes on the same tone.
- Whilst the amp is an important part of the tone, you have to take into consideration the guitar being used: a tone setting which works well for a Les Paul may is not going to make you sound like Slash if you are using a Tele. Also, the pickup switch controls and tone controls on the guitar matter.
- What you hear on any record is NOT the amp tone. It is the amp tone after being coloured by room acoustics, a microphone, a pre-amp, and any console EQ, plus any mixing and mastering compression, EQ and other manipulation. It’s also in the context of a full mix which sounds totally different from the isolated tone.
- The tone you hear on the record is, to a large degree, influenced by how the guitarist plays. It is often said “tone is in the fingers”. You are never going to sound like Duane Allman until you learn to play like Duane Allman did. A lot of people get frustrated with patches or with amps because they can’t get the sound they think they should, and a lot of that is down to playing style/technique.
The bottom line is: don’t try to replicate the sound from specific records too hard. It’s a rabbit hole that you can waste a lot of time and effort on, and develop a lot of frustration.
Learn to use your amp and you should be able to dial a bunch of great tones in yourself.
For classic blues, I would start with the crunch setting. Set all the EQ to 12 O’clock and all of the FX off. Then play around with the gain, as well as the pickup selection on your guitar. If you need something a bit grittier, do the same on the Lead setting.
When you are close, then mess with the EQ a bit. Remember to listen to some reference tracks to get a view of where you are aiming, but also remember you aren’t going to replicate these tones exactly for the reasons I listed above.
If you are going to add FX, then start with some reverb. And then some delay.