I started this topic a while back:
I’d call my self a fast-twitcher. I’m not track, sprint level 1800 watts but back when I raced, I was always a good sprinter and finisher and couldn’t climb worth crap.
The hard part of being a fast-twitcher is finding the events that you are training for. At 55 years old, I’m not going to ride crits anymore. I want to do fun group rides, fondos, gravel, etc. and these are not short fast twitch events. 
Still, I just hit a performance peak and have been riding with a new group at what feels like above my level.
This last fall/winter I just did a ton of Z2 and almost zero intensity. I’d mix in short tempo/SS intervals just for fun. In the spring I started with a SS block and got good gains (like +20 watts after all that Z2). Then I did a VO2max block and after three sessions I was dead. I rested for a couple weeks - back to Z2 and then tried VO2max again. It went a lot better. I played around with hard start, high cadence intervals. I think the high cadence works well for me because it induces a higher heart rate, more sucking wind, less torque, and less muscle fatigue.
What I found out is that I don’t need a lot of intervals over threshold or even a lot of SS. Above threshold is already my strength. Despite being a slow, old geezer, I have 3 pages of Strava KOMs all under 8 minutes with most even shorter in the 30 second to 3 minute range. My short power is relatively much better than my 20 minute power.
After the second VO2 block, I thought I’d try some sprint (10 second) intervals. The first session of 6x10sec crushed me and left me with DOMs for 3 days… I started doing those 10 second sprints at a lower power and then just sprinkling them in my rides (like 2-4 of them).
Like I said, I’m really happy with my performance lately. What would I do differently next year? I think I’d do a longer time in zone tempo/SS progression coming out of base. I seem to respond to 85% which also feels fairly easy.
It seems like raising my FTP is my Achilles heel. WKO5 says that my FTP is at 86% of my VO2max. The “raising the roof” part seems to be difficult.