I will admit I actually avoid turfing lately. I find more fun to be had in the ranked modes, as people are focusing on maximizing their weapon's specialties in ways that Turf Wars will not.
Keep in mind that each type of weapon will have a specific area or expertise, so to speak. Some weapons may not have a high kill ratio but provide massive value in area denial or coverage. Splatlings are a great example, a weapon that can kill well in the right hands, but excels at annoying enemies by drenching the area around them and pinging them with a few bullets if they're at near-max ranges. Right now the three main long-range splatlings have different areas they focus on, such as defensive (deco) and denial (splatling). Hydra is a hard one to master right now, the long spin-up gives you issues when you don't have good flank support, but with a good team of people you can absolutely center-control maps with that weapon, using your splashdown to counter anyone closing in for the 'easy' kill.
I don't tend to use the practice range myself, but I'd use it to gauge specific testing aspects. Bomb throws are a good example, you want to practice 'rolls' with splat bombs as well as accuracy for landing on raised platforms (good for tower control). If you're not familiar with the roll, it's throwing a bomb so it taps a floor edge early and finishes its arc exploding at the target's feet. Any contact with the ground causes them to set their timer, so you can even 'roll drop' off a ledge to hit someone beneath you that may be coming up. Suction bomb practice should include nailing very specific spots (such as the tower's control pylon), while burst bomb practice should be the 'two tap' for aggressive weapons. Two-tap is essentially throwing two bombs to do a chip/direct hit which should OHK anyone done right. If not, you'll have at least pinged them down and inked around them for a finishing shot from your main weapon. For curling bombs, practice the cooker (holding it for a specific range/explosion) or the bounce, as you'll want to know predictably where the bomb will end up at the end of its run. This is extremely helpful for retreating enemies, as you can sometimes bounce it off a wall behind them for a finisher. If you're using a sprinkler weapon, knowing the range of the sprinkler and how it inks can ensure you put them in annoying spots that get the most coverage, powering up your special faster.
The range is also good to gauge how your special charges up or how it performs, such as area of coverage or knowing how much damage you can reliably do at a given range.
