Don't concern yourself about asking stupid questions. At times I believe I'm the resident queen of stupid questions.
If I understand your example correctly, you placed a max proxy bid of $20 on eBay which placed you as current high bidder at $15.
...."When you place a maximum bid on Auction Sniper for an auction item, is it the same amount that you placed at the auction itself"....
Setting a snipe for the same amount you've already bid is of no value. You are already covered up to $20 with your eBay proxy bid.
...."or another higher amount that will allow Auction Sniper to exceed that maximum bid in increments of $1.00 (or whatever the increment would be at that auction)yet set a limit that Auction Sniper can not exceed? "....
If you are really willing to go higher than $20 for the item, set your snipe for the maximum amount you are willing to pay.
...."To ensure that I have the winning price, should I place a higher price on my Auction Sniper folder for that item?"....
Again, set your snipe for your true max. It doesn't ensure you win the item, but doing this prevents other bidders from knowing that you're waiting out there ready to snipe with a higher amount.
..."Also, if I place a higher price say $25.00, and someone outbids that amount, would Auction Sniper automatically place a bid at $26.00 in order for me to win that auction?"...
No, Auction Sniper bids only the amount you've set. Nothing more, nothing less; i.e., if you set your snipe for $25 and the next highest bidder is $22 at end of auction, you win the auction at whatever increment is just above $22.
There is a feature here that I don't have a crystal clear understanding of, and that is an Auction Sniper email alert when your snipe amount is not enough to win the auction. I don't think we are guaranteed an email notification. Perhaps Adam R. can give us the definitive on this.
As I've read over and over from veteran snipers--An essential key to sniping is to determine what your true max is. Then, use that amount to snipe with.
Personally, I never place any bids on auctions that are really important to me. I just set my true max for the snipe amount and watch. Once in a while I may raise that amount if the bidding goes higher, but not often.
As you can see, I'm not very concise. I hope I've been more helpful than not. There are other more experienced veteran snipers here that might be able to clarify the answers for you. Don't hesitate to ask.
Neva