Super strength shapewear?

[PalacePalacePalace]

I've got a special occasion coming up getting married but don't tell anyone

I have a lovely dress but I need something to hold my tummy in and to smooth lumpy thighs. I need to wear my own bra.

I've looked at the all in one suits with legs but am not convinced that it'll work. Plus how do you go to the loo???? maybe it's safer not to ask

Could I wear separates eg a waist cincher with long leg shorts or tights?
Are Spanx still well regarded? Any other brands I should look out for?
I'm a 18 and willing to spend money to get the right thing.