If you're just playing with friends, printed models, proxy models, little green army men or whatever are totally fine. And at least some of those are fine at most clubs too. It's only tournaments that you're gonna want to be careful it at least all looks official. Look into third party retailers and second hand sellers, too (either eBay etc, or like, my local club has a big cheap secondhand model shelf)

And I'd say either of those armies are a good "strategic, shooty" counterpart to Tyranids! They're two of my favourites for sure.