In my Opinion

1. Wash
2. Dry
3. Clay
4. 3m IHG or Moms Step 2
5. 3m SCLW or Moms Step 3 or any other LSP

You could use either Mothers Step 2 or 3m IHG, i guess it depends on your preference, for me 3m IHG has more shine but a lot harder to remove though especially when left to dry, Mothers Step 2 has a little less shine but has filling properties than can mask and conceal swirls and very light scratches.

What i do is first use Moms Step 2 to hide the swirls, and then if its good i go straight to LSP, if im not happy with the results however ( not enough shine ), i put on IHG or Megs 7. After a month or so, if the swirls are still masked and hidden i skip Moms Step 2 and go straight to IHG or Megs 7.

As for the LSP's, If you're gonna use the 3m IHG i would recommend you also use the 3m Show Car Liquid Wax, since they work quite well together and it also comes in sachets at the same price as the IHG in Ace the last time i bought mine. If you're gonna use Moms Step 2, then better go get the a Moms LSP since its also made to work with each other.

As for your topcoat or carnuba concern. That would depend on how much time you have, how often can you wax your car, and how well pampered your car is being one factor. And for aesthetics, whats your car's color being another factor.

If you have enough time that you can wax your car, 1.) Once every 2 weeks, if its a daily drive without parking area cover, OR 2.) every month if you car is parked in a covered parking area and well maintained since you use Showtime, then i would recommend using Moms Step 3 Pure Carnauba. Moms Carnauba works well in giving a very wet look to your car but the protection it offers is shorter than compared to Top Coat. Works well with yellow-orange, yellow, red and blue cars.

If you have a daily drive without parking area cover and only have time to lets say apply LSP every month especially with the weather nowadays. I would recommend you use Top Coat. Top Coat gives a very clean mirror like crisp shine, but its looks is very synthetic though not as wet as Moms Step 3 (its synthetic anyway). Top Coat works well with very dark paints, especially black and Dark Grey, it will give you that sleek shine especially if its spanking clean in broad daylight. Based on my experience, Top Coat usually lasts about up to 2 weeks longer compared to Moms Step 3.

If you have a preference over Mothers Products, i would also recommend you get a FX Spray Wax (Lighter Colored Car) or a Reflections Advance Spray Wax (Darker Colored Car). Use a little after your weekly wash and dry routine and buff with a MF towel. A bottle of this goes a very long way, i use only 2 sprays per panel 3 on the hood. This would really extend your LSP's protection and durability especially nowadays with our weather, enhance the gloss of your paint and give it that newly waxed feel. And then just use Showtime for quick detailing touch up and clean ups during the week.

Hope this helps.