Essentially, there are three parts of a solve: recognition (lookahead), solution (efficiency, or in other words the movecount of the solution) and execution (turns per second). Here are 2 videos I reccomend for lookahead and fingertricks (turns per second).
As for efficiency, that is my weak area. What I know that might be of your interest is pseudo slotting, but the recognition is dampened here.
The best cubers for each area to me:
Lookahead: Max Park
Turns Per Second: Ruihang Xu
Efficiency: Tymon Kolasinski
Go watch the reconstruction of Tymon's solves, I mainly get that from a youtube channel caller Lazermonkey.
Extras:
X-cross (short form for extended-cross) is something that you may want to look into. I will link a video below:
Additionally, I found this very good categorisation of the possible approaches for x-cross from a comment from another thread:
1) seeing the solve for the 2x2x2 and one other cross edge during inspection, with intention to locate and place the 4th cross edge during the solving phase.
2) seeing the solve for the 2x2x2 during inspection while making sure that the solution for the 2x2x2 puts the other 2 cross edges in a "good" position. A good position means easy to solve in relatively few moves.
3) Seeing the solve for the cross during inspection that either builds or preserves a c/e pair. For these solves you usually know how to place the pair during inspection as well.
4) Seeing the solve for the cross and one corner during inspection, with intention to locate and place the F2L edge during the solving phase using keyhole.
5) Seeing the solve for the cross and one F2L edge during inspection, with intention to locate and place the corresponding corner during the solving phase using keyhole.
Lastly, check out these x-cross examples by feliks himself, and try to understand the logic for each of his solution provided:
In this blog, I have 25 scrambles sent in by a CubeSkills member, and my solutions for the extended cross (or cross + first pair) on each of them. This blog is primarily aimed at advanced 3x3 solvers.
www.cubeskills.com
From experience, you should not put x-cross as a top priority, especially if you don't have any experience in blockbuilding. I did attempt to solve x-crosses for every single solve for a period of time, and my movecount just surged because I had to preserve pieces here and there, as well as given the limtied time of a 15-second inspection I could only stick to inefficient solutions. X-crosses only serve you well when its the right time to take advantage of it, and in the x-cross video will show you when it is the right time.
(Keyhole) Also, there was this term 'keyhole' mentioned in the list above. Check the video below out:
Pseudoslotting:
This is something very advanced, but will get your f2l movecount way down. Keyhole is related to this technique as well.
One important general piece of advice: Go slow to go fast - once you learn a new technqiue or concept, dont go straight into timed solves. Go for casual solve, like sitting on a couch or maybe while waiting for the food to be served at the restaurant. You need to familairise yourself with the new technique, and it takes time through repeated
unconstrainted practices (in other words untimed solve).