Mudlite Ats would be a decent mildly aggressive tire that are close to the same weight as the stock tires. I had a set of those on the rear of a 2wd 250cc Suzuki Ozark and I couldn't tell the the difference in power over stock tires but it definitely made a difference in how well it did in the mud. Priced pretty reasonably too, I'd stick with the stock 25x8x12 fronts and 25x10x12 rears https://www.amazon.com/Full-ITP-25x8...lite+atv+tires
Kenda Bearclaws are another good choice for all-around performance and value But are slightly heavier than the Mudlite at's. https://www.amazon.com/FRONT-25-8-12...6T1X1T62GFTX99
One more I'll throw in there would these tires https://www.amazon.com/Tires-25x8-12...C739QN9WBVXT09
. They're a little deeper tread than the other 2 but slightly heavier. I think the Mudlite at's would be the best choice overall because of the light weight and still relatively aggressive but not too aggressive tread pattern. Yamaha even made them the stock tires on the Big Bear 400 the last couple of years it was produced.