With the active cooling of the Tibetan Breeze kit you ordered, you should be good to go - it will eliminate the fade. I would not recommend changing out the coils. I would instead look at optimizing your current setup to correct the coil performance:

1. Check EOS isn't triggering before flipper is at peak (use switch test and manually move flipper slowly and note when EOS triggers - adjust if it's before the flipper is at peak)
2. Check coil stop (REMOVE it and try to move the middle - visual inspection sometimes looks good when it's not)
3. Check coil sleeve for free movement.
4. Wax the playfield with a carnuba wax like P21S. Buff with lambswool pad.
5. Check that flipper switch blades at the flipper buttons are making solid contact when the button is depressed (both levels if there are 2 flippers on a side) instead of BARELY making contact which can cause the coils to flutter power and feel weak.
6. Check coil resistance with a multimeter (ohms setting) to make sure you don't have a bad or out of spec coil robbing you of power.
7. Check power settings in system menu for coils. With active cooling, you can afford to turn this up to give more power. (you did this, but for posterity's sake of other people with the same idea, adding to the checklist).

Here's a Stern coil strength chart, most to least (part, resistance in ohms, windings, wire gauge):
090-5020 3.4 900 22
090-5032 4.3 1080 22
090-5030 5.1 1100 23
090-5025 9.5 1570 24

For your vertical ramp, slo-mo it with a cell phone video and see if there's something about the ball entry that's robbing it of power.

Do this instead of changing out coils. Too-strong coils break stuff faster. Not a good idea, especially since you now have the active cooling covered to keep the performance consistent once you get it dialed in.

I think it's very unlikely to blow a node or coil (they don't customize node boards per machine, and this node is in other machines with bigger coils), but it CAN break stuff on your playfield with stronger shots than it was designed to handle.

Wax is a great suggestion I forgot. Too obvious. D'oh.

The damage to playfield components from too-strong coils doesn't happen immediately, but over time. If you turned the power down, that's good, but using the stock coils and doing the stuff on the list probably would have achieved the same result with less wear and tear on the machine over time.

But it's your machine for YOUR amusement to do with as you wish.

Godzilla uses a mix of coil strengths, where TMNT uses the same coil size for both flippers. That may be where your perception of comparative weakness is coming from. It's also good to check the resistance of your coils when they're dead cold to make sure you don't have a defective coil for the strong one on GZ and the weaker stock coil on for the other side, giving you the perception of two weak coils.

Also, look carefully at your flipper switches inside the cabinet by the button. If that contact point (looks like a dot on the end of the switch blades) is uneven, it won't make good contact (poor/not full surface area), even if the blades are close enough for it to touch properly, and will make the flippers feel weak.

I'm not aware of flipper coil differences in Pro and Premium trim levels, just differences between actual different machine models (i.e. GZ to AIQ, Maiden to RUSH). It's up to the designer which coils he feels the machine needs.

The diode (either physically one the coil or on the board that drives the coil) is just to make sure that current only flows TO the coil and doesn't surge back up the line and damage the components it's connected to.