About the cascade mod: if you're thinking TMB into Normal, that’s usually the preferred route since the TMB channel has tone shaping and more gain stages to begin with. Doing the cascade can push the amp into a heavier, more saturated tone—think late '70s rock pushing into early '80s hard rock territory. With the right tweaking, you can even get into early metal territory without pedals.
Also, if you're after just a bit more dirt without totally changing the character, your idea of upping the gain in the TMB channel (swapping the cathode resistor/cap or tweaking the cold clipper) is a solid move.
While I was tinkering with mine, I also spent some time messing with classic
android game mods like Traffic Rider—it’s a different kind of fun, but still scratches that “builder” itch between solder sessions