I think you "can" but it will look pretty squished/cramped. When I was touring parade homes last year, some master baths had whirlpool tubs without much deck, and they really looked squeezed in, making the bathroom look crowded rather than spacious. In my mind it was a detractor to the look of the room. Of course it does make a difference how the rest of the room is. If it's a small room to start with, and a tub with a small deck is to scale with the rest, then you'll be ok.

If against a wall, I try for about 12". If against a window I'll sometimes do two tiers. The higher shelf essentially becoming the window still, and the lower tier being the tub deck. For open sides, 8-12". Those numbers can be adjusted if a drop in versus an undermount tub. With an undermount you don't want to go too big or the tub can seem like it's a hole off yonder in the distance. And yes, it depends on how the space will be utilized. Plants, candles, jars of bath crystals, a keg of beer. Mongo

The easiest thing to do is to remove the old faucet and measure the hole to hole distance to see if it will fit. What is the surface material that the faucet is mounted on? Some man made materials can be modified to cover the holes. If the surface can't be modified then purchase a faucet that will cover the holes.

The size of deck screw to use will depend on several factors, such as the thickness of the decking boards, the type of material you're using, and the load requirements of your specific project. As a general rule, the diameter of the screw should be at least equal to half the thickness of the board. For example, for a 32mm thick deck board, you would want a screw with a diameter of at least 16mm. This will help ensure that the screw is strong enough to hold the board firmly in place without splitting the wood. In terms of length, you'll need to consider the thickness of the deck board, the depth of the joist, and any additional layers of materials you may be using, such as flashing or ledger boards. As a general rule, the screw should be long enough to penetrate the deck board and the joist by at least 25-30mm to provide a secure hold. When selecting deck screws, it's important to choose screws made from high-quality materials, such as stainless steel or copper, which provide excellent corrosion resistance and durability in outdoor environments. You can also choose screws with different head styles and coatings to suit your specific project needs.