In all honesty there aren't many lizardmen feats to go off of at all - I built the entire notion of the geomantic web off of that one time Mazdamundi put a mountain between him and the Druuchi and TWW2's implementation of it, for example. But yeah, there are avenues for you to do biological fuckery. If you're ever uncertain, just ask.
Yep - obviously when you're more of an active space empire because that's the point where it starts to be practical to ask them, but it's possible.
They actually all have entirely different tech trees from you and each other. This comes from the very earliest days of me designing this quest, where I had two prospective routes and main characters you could have taken: Mazdamundi, which is basically what the quest is now, and Kroak, who had a structure that was basically 'all the elder slann go wander around the cosmos doing slann stuff' and it would've been a lot more centered around actively searching for the Old Ones. Eventually I decided not to do it that way since it was too complicated, and used the remains of those ideas for the system we've got now. So that's the meta reasoning, but there's fluff justification too.
They share a few key techs with you - spawning pools, mind fog breakage (which is more of a thing for them since they're away from the Web), etc, that they mostly don't have the facilities or time to actively figure out - none of them have a spawning pool to examine while they're off doing their own thing, for instance, but the knowledge is transmitted through the Communion once you complete the tech. Aside from that, they're mostly busy doing their own quests and developing down their own specialized routes - Chaacalot goes a lot into mind controlling legions of soldiers, massively-scaled illusions and the like, and is probably the most active diploslann since he can make minor polities do pretty much whatever he wants with his powers. Zaqunda eventually turns into something resembling a high magic necromancer, which combined with his defensive magic specialization means that it's tough as hell to even kill one of his guys, and if you do they just get back up. Adohi-Tegha has his subfaction turn into something akin to Eldar farseers, where they intervene at significant events with exactly the amount of force needed to affect something across the galaxy which was his real target all along. Huintenchiuli gets magitech robots and a bullshit space armada, and is probably the second-most diplo focused elder slann. Kroak, meanwhile, eventually just goes straight-up Seraphon and creates lizardmen daemons out of purified essence and stuff like that.
So they each have a path to develop down, it's just the commonalities between them that you help unlock.
I'm the person least able to accurately predict my own writing speed, but this is probably correct.