I actually wonder if it is better to do what I said I wanted to do above, or instead leave the highest bid with Gixen (because it bids really a few seconds before the end), and I could bid just a bit earlier, and a little bit less, so if somebody tries to outbid me after my bid Gixen can outbid them?

Yes, but possibly you will also make them to drive the price up.

For instance if the top bid is in this moment $60 and you put $100 in Gixen.  The person who has the $60 bid may actually bid $90, if you bid manually $95, they may decide to up their bid and anybody else watching the item will know that they have to snipe with at least $100,.  If several people bid $100 in the last few seconds, it is the one who bid that amount first who wins.