I’d recommend starting with the lightest weight synthetic thermals you can find (silkweight). These should be the only thing you wear under waders or rain pants. NO synthetic pants.
Merino wool is great for your upper body and absolutely sucks for your lower buddy, when worn under waders/rain pants.
Waders: use a light weight wading boot. For example; Simms Flyweights, along with the Simms Right Angle Inserts. I would only wear these if you’ll actually be walking through boggy areas, crossing rivers, etc. If you’re just dealing with rain. I think rain pants are more versatile.
Rain Pants: use high quality Gore-Tex pants. Preferably avoid hunting brands (Kuiu, FIrst Lite, etc). Arcteryx and Rab are good choices. I would wear these if you’re dealing with sustained rain and walking on firm ground.
Synthetic Pants: if you’re just dealing with intermittent rain, I’d forego waders/rain pants. Don’t be afraid to get a little wet. These pants dry relatively quickly, while walking. A good example is the Kuiu Attack pant. NO need for thermals under these pants.
If you’re on a moose hunt where you’ll be mostly glassing for moose, consider bringing a tarp that you can pitch with trekking poles, that’ll allow you to glass from underneath, during light and intermittent rain that still allows enough visibility for effective glassing.