1) It can be very difficult when figuring rewards on both the lend and borrow side of Aave as they are variable. Personally, I borrow a small amount of USDT and have noticed that while the Matic rewards are variable, they are typically higher than the interest. The risk is that Matic token could drop in price and end up being less than the interest. It's probably a good idea to keep an eye on it to make sure that your Matic rewards justify the borrowing APR.

2) I'm not sure why rewards are paid in WMatic. It's the same on Curve and Aave as well. The good thing is that trading to Plasma Matic costs almost nothing on Quickswap or Sushiswap on Polygon. I sometimes swap my WMatic for WBTC or I will stake it on Beefy Finance. I'm also testing out Polycat.

3) I would love to have a good tracker. On BSC, I use YieldWatch and it works well for the platforms that it supports. I wish that someone would come out with a similar solution on Polygon. I haven't paid for APY vision and I too would like to know those figures. I'm frustrated that I don't know what my SLP is worth on Sushi. I think that Ramp Defi is coming to Polygon and they have a unique DeFi solution and a really good interface. I do some yield farming on BSC through Ramp and think that it will be great when it comes to Polygon.