Test driving, down payment questions

Alright, so I have been saving for a sizeable down payment for a new or barely used 4runner. I haven't driven one with kdss and want to compare it to the limited and trd pro. I'm mostly certain the orp with kdss is where I want to land but want to experience the on road feel before making my decision. That being said, I have no desire to purchase just yet, I just want to be sure I have my general price ping and down payment planned out. Is it rude of me to test drive now knowing it'll be a year or so before I purchase?

Second question is... Is it better to put down a huge down payment or to just use that money to slowly pay down a loan? I have excellent credit (790+), zero debt other than placing groceries on a cc for points and am shooting for a $20k down payment. I ask because using that full amount doesn't seem to lower a monthly payment significantly.

I do plan to own this car for many years and will be purchasing, not lease.