PATB-1b is actually higher output than the JB... It just doesn't sound like it because it has less mids. But it goes into crunch faster when pushing semi-dirty amps. JB is all screaming midrange. Both are great at what they do, in the right guitar. I replaced a JB with a PATB-1b in my Ibanez RG570 (basswood, sounded flubby with stock SH-4 JB in the bridge no matter what I did). My Ibanez turned out to only like the PATB-1b in the bridge.
No shortage of amp model choices, depends on what you are going for.
TLDR: Placater Dirty, Brit 2204, Brit P75, Brit Trem Normal, or Plexi in probably that order of reducing gain (P75 is around same as Trem or Plexi, but is punchier).
Placater Dirty for Friedman HBE-100 modded Marshall goodness. I tend to just stop there.
Line 6 2204 Mod is another fun one, though I tend to get into trouble with the parametric EQ.
Brit 2204 is a classic JCM800.
Brit P75 (Park 75) is often overlooked, amazing punchy classic Marshall.
Plexi Jump is terrific, if you understand how the controls interact. Or just go for the Bright or Normal channels if that's how you like to use it.
Brit Trem is a Marshall 50W Plexi, if the other actual Marshall models strike you as too harsh it's an excellent choice.
Brit 45 is a JTM45, great for Hendrix, classic AC/DC, and so much more.
Back to non-Marshalls, Derailed Ingrid is a Trainwreck Express with EL34s, not really a Marshall, gets very compressed with gain up, but at lower gain does some Marshall-like things.
Line 6 Doom is a JCM800 pre into a Hiwatt power amp, tweaked for more gain, rich sag, and lots of bass.
German Mahadeva is a Bogner Shiva model, which is a pretty modded Marshall sort of amp. Treble control doesn't behave at all like a Marshall.
And of course there's a slew of amps commonly mistaken for Marshalls on records: Soup Pro (Valco Supro S6616), Tweed Blues (Fender Bassman), US Princess (Fender Princeton), US Small Tweed (Fender Champ), US Deluxe (Fender Blackface Deluxe Reverb), Fullerton (Fender 5C3 Deluxe), and Grammatico (Fender 5E3 Deluxe), particularly when paired with a Celestion speaker and a fuzz (Legacy Jumbo for Led Zep I) or overdrive. [Stay away from the Fullerton & Grammatico jumpered channels though, they tend towards blocky fuzzy chaos. Fun if that's what you are looking for, but you probably aren't if you are looking for Marshally...]
And wandering outside Marshall-adjacent tones:
Line 6 Litigator sounds pretty amazing with anything, but I really like it with the PATB-1b. Smooth, yet varied texture with pick attack. Great for low gain, and can do smooth singing high gain when pushed with fuzz/OD/compressors, I tend to use a KWB a lot.
For metal, the Revv channels & Archetype Lead (PRS Archon) are surprisingly dynamic and hard to get bad sounds out of. PV Panama (5150 lead) does exactly what you'd expect.
One trick for classic EVH, Blackmore, and Gibbons tones is to use the Retro Reel modulation (I usually set Saturation around 1.5, and lower or zero the Wow Fluttr parameter, can lower Tape Speed to emphasize midrange) right in front of the amp. Warms things up without getting mushy, much like the various Echoplex & reel-to-reel preamps they used. Not a clean boost, not hugely dirty, not hugely compressed... Just sort of more-ish...
Playing with the various power amp controls is very powerful on the Helix. Sag & Bias in particular. Lower Sag for tighter sounds, higher Sag for more power tube distortion. Bias & Bias X affect cold vs hot bias sound/feel, and what happens when it's pushed hard. All very interactive. Lower Sag & Bias for clean & punchy, raise for warmer power section. I tend to use snapshots to tweak them low for punchy cleans, higher for crunchy rhythm tones, very high sag for smooth leads, and low sag but 6-7 bias for tighter leads.
Hope that helps more than it overwhelms!
