Multisportdad, welcome to the site. Good (and difficult) question to jump in with. This topic can be quite controversial and one to which you will get a very wide array of opinions and points of view.
There are more than one hitting philosophies that can work. There are some things with hitting mechanics that are generally considered a constant and some that are optional, depending on style, preference, natural tendancies, etc. Also, there are teaches that may be appropriate for one age/performance level that may not apply as well to another. There is even quite a bit of conflict on how early and how often a hitter should get instruction, as you will quickly see here.
As example, I somewhat agree with the other posters that you don't need to go overboard at an early age. I also like to keep natural elements in the swing, as 2022OFdad suggests. But, at the same time, many kids' "natural swing" need adjustments in order to be able to perform efficiently against better pitching at higher levels. I have had countless kids come through our HS program who had swings that could kill it at sub-varsity level but would be exposed against better V pitching. Also, by the time the player gets to our HS program, if his swing is too far off, he has a very difficult uphill battle to face. So, some earlier evaluation and any necessary work and adjustments can be quite important.
And, regarding frequency, I disagree with others here that you only need to go when you are struggling. Almost every hitter I have ever seen and/or worked with has some area that is chronically deficient and requires more than just being pointed out and corrected on the spot. Most young players are not disciplined enough to then go home and work repetitively enough to make the adjustment permanent. Somewhat regular work and monitoring are necessary. Also, a hitter typically advances through stages. If he has someone who is monitoring and helping him work through levels of advancement, he will likely progress more quickly. I generally like a balance of periodic instruction combined with good notes and homework.
Regarding your question #2, I do agree with 2022 that the best teach, particularly with young players, focuses on being on time and on plane. That is generally taught by both old-schoolers and new age guys (except those particularly promoting loft).
Regarding your question #1, I would be quite surprised if a 2024 has outgrown the instruction of a well respected coach with the qualifications you describe. He may not be using all the available measuring technology, etc., but he is likely putting your son on a good path. And, the fact that they connect is valuable. My suggestion would be - as your son sees other teaches and he begins to question, he should just ask the current instructor. His answers will tell you and your son what you need to know, one way or the other.