Welcome to the fam!
Can't comment on the Sufferfest as I haven't used it but this is what works best for me:
Trainingpeaks premium - you can find coupon codes online for a discount on the yearly sub - it's worth it IMO as I use it to plan all my workouts using the calendar - the ability to drag n drop/copy pasta workouts is great.
Then I purchased a 3 month structured training plan within Trainingpeaks. Did an FTP test (in Zwift), did the 3 month plan, re-did an FTP test and started the same plan again by copy/pasta'ing it with my improved FTP test. That has worked great for me.
Zwift - I use this as my riding platform. Once linked to Trainingpeaks, your workouts appear in Zwift. I find that Zwift helps with the gamification/social aspect as it somewhat removes the monotony of indoor riding. Plus if you're into racing, you can do Zwift races/events.
Some folks swear by Trainer Road but I haven't used it so can't comment. I also find that the structured workouts which Zwift has are not great, hence my suggestion of using Trainingpeaks.
Shout if you get stuck 😁