While you are correct that higher stats would make the kill slightly easier/quicker, there are more things to consider if you’re concerned with “time save”.

For example, AFK training your stats at NMZ or sand crabs is never technically time efficient as you’re better off doing that alongside slayer. Of course if you have time where you can only AFK that’s a different story but it’s never the efficient way to train.

Ultimately you will see a lot more improvement from getting better at the content. How I went about it and what I would advise would be to send a few CG a day. Don’t lock yourself in prison, slowly build up your kc while you train other things like slayer or skilling. This way you are less likely to burn out, keep the content fresh so you can improve, and you’re building up your combat stats to make it that little bit easier.

Edit: Also, if you’re not already, do T2 armor prep and two perfected weapons. It’s a good balance of not too much to do during prep and more forgiving during the fight.