Hey, I once half jokingly tried to route this game but gave up once I learnt that most speedrun sites don't allow h-games. Just this page existing brings a smile to my face for the possibility of h-game speedrunning. So, on that note.... Can I have a link to a patch that changes the h-scene CGs to "streamer mode" and, if a similar patch exists for other Rance games, those too?

The streamer patch is available when purchasing Sengoku Rance from Mangagamer. It shows as a downloadable file along with the main game. AFAIK, there's no streamer patch for 6. I hope that the upcoming English release of Rance Quest has a streamer patch.

Can you use an autoclicker to speed through the dialogue or do you just click for yourself?

I just skipped the text myself with the ctrl key but dont think it would be a problem to allow for an autoclicker to skip the text instead.