One of the unexpected benefits of Sonic Mania for me is that it finally got me to start liking Sonic CD. Playing the levels that made it into Mania gave me the idea to go back and give CD a real try (I only played it through once I think). I usually would start it up and turn it off in the second zone because its so unlike Sonic 2/3 to me. This time I actually tried to look at the time travel mechanic, the music, and the odd level design with an open mind and I ended up really liking it. Played it through three times at this point, I'd probably even put it above Sonic 1.
I still kinda hate the jump sound effect
Also, I appreciated Mania's visuals even more after spending a ton of time going back to 90s Sonic.
The trick is to jump frequently around turns. Your turn radius is tighter when jumping, and Sonic will rocket off in the direction he's facing after hitting the ground. Using the stick/dpad to turn left or right is more useful to direct Sonic to pickups on straightaways.
I love the special stages. They grant the player a great degree of control and decision-making, especially compared to earlier special stages in the series. I'd play a whole game full of them.