There have been a lot of debates on the effectiveness of high pinpoint damage weapons. Personally, I find they help my playstyle. The splatter effect of smaller weapons can be largely negated by using Precision Shot a lot, but I find that to be a bit limited to rely upon completely. Without that you are relying on overwhelming firepower and I prefer not having to strip all the armor off of my enemies.
It's not exactly relying on higher firepower (although sometimes it is), you can have much higher firepower with big hitters and still perform a lot worse than with smaller weapons for the same alpha damage, depending on the damage needed, and some smaller energy weapons get much more benefit from Thermal Exchangers than bigger guns.
Also can happen the opposite, it depends on the needed damage for a specific scenario. You may actually need more for firepower with bigger guns to equal chances to kill at 0-20%, for example. So in principle not any of them is inherently better... but then you add on the fact many smaller weapons are much more damage/weight/heat efficient than big hitters. Still a big factor are the exact damage thresholds and how much damage is wasted for the combinations of hits which allow you to succeed.
And as a separate issue from that, smaller weapons are more predictable with more than one consecutive salvo. One big hitter and the equivalent in smaller weapons may have very a similar chance (to kill) at some particular threshold damage at a specific location (usually head of CT) but even in that case the second will tend to be more predictable with a follow up, because if you don't succeed it is way more likely to do significant damage, while the big hitters are more an all or nothing kind of thing, depending on the weapon (not the same an LL than an AC20 when comparing them to a ML).
I would not put a large laser on the LRM boats. Their purpose is to lob missiles. A couple of medium lasers is good for back up, mostly because of how easy it is to spare another ton or two for them. I have used mixed builds, but LRMs are more of an all or nothing weapon when it comes to most loadouts.
With weight to spare I'd use it for better cooling or even JJs. A couple MLs are not going to do much if it comes at that point, it's not like they are a couple UAC20s. Add a couple TTS+++ instead, that will help to nullify the close range penalty and will make the build more consistent against lighter mechs.
A mix of pinpoint and spread damage is generally better than completely relying on one or the other.
I think it is the opposite, that the best results come from sticking to one of both types. And for small weapons in particular. They scale much better than bigger guns with multiple salvos, but if you start with very few hits you won't get that scaling, you need some critical mass.
Yeah it's not happening don't worry. At most a M laser or two but never anything more "intense" than that.
Like said above the perfect complement for an LRM boat are TTS+++. A couple of them and you'll be able to alpha full force at close range (negating the close range penalty) and also will improve your consistency at medium range against very evasive foes and at very long range (where you have long range penalty) against most foes.
Having a consistent high base chance will make easier to plan ahead. If for example you know you can one salvo kill some X type of foe (usually a soft target like a vehicle or a light mech) with max chance, having this aspect secured and not having to worry about range penalties or evasion may allow you to ignore that foe for a while, because you know you can kill it at any moment if the need arises.
I tend to favor vanguard pilots - bulkwark and tactics. Reserve to the end of a turn, then jump in, jump out again with initiative, or jump into cover to get the defensive bonus.
I don't think Vanguard makes much sense for a non-assault mech and for the tactic you describe AP works way better. Reserve into phase one, PS and push the target one init and next turn PS again, with optional jump out afterwards.