I'd always go for one level myself, given that all my guinea pigs are lazy artcles !
Years ago, my Dad made a big outdoor hutch from a heavy old sideboard (divide in the centre, hatch in the floor of the upper level, heavy wire mesh to ventilate ) they had a ramp but it was carpeted, shallow and had a side so more like a tunnel.
I had 4 females who happily used them (2 pairs of Mum/Daughter)
My piggies now wouldn't even look at a ramp except to hide under it.
You need to get a big enough hutch to give a decent sleeping area . I have a Gumtree bargain rabbit hutch in our Pighouse for GP6 , there's a door cut in one end, leads to his floor area.
GP7 and GP8 have two houses - one wooden box that is designed to fit on a run, and a cardboard box (Costco bread one)
They have a C&C divide in the Pighouse (old wooden playhouse)
C&C are good for indoors, you build it to fit the space and how many pigs. IIRC each panel is 14" square, I use cable ties to fasten and put thick cardboard on the floor over the grid. Some owners do lofts/ramps, I don't.
Any outdoor hutch needs to be positioned in a sheltered spot, away from direct sun, damp, draughts, free from the risk of predators.
And check the bolts (add a couple more) and the mesh (add another layer).
You can put a thick plastic cover over the front , well ventilated. The hutches tend to be shallow, guineas won't sit in rain so it seems a shame to have them cooped up in the sleeping area.
We painted our rabbit hutch atfter we deep cleaned it (steam gun + VirkonS) , DH added flymesh and more wire when we used it joined to their run.
I can't get it out the Pighouse now (had to take the door off to get it in) so it won't go back out.
Be aware of the height of the hutch, they can attempt to jump , they don't check how high they are 