The catch for this though is the you need high range on the BFC for accuracy versus missiles and targets because of how range effects accuracy in terms of scaling if your railgunr ange is 10,000km you need a 96,000km range bfc to get the majority of the accuracy out of it, a 48,000km bfc for example would mean accuracy drops to around 75% at 10,000km
It's actually closer to 80%, but if you double the range (and BFC size) you gain only +10% accuracy so there is a diminishing returns aspect. Similar to ship-based PD, there is a point at which you benefit more from adding extra weapons than from using the same tonnage for bigger BFCs, and this applies for fighters as well, especially since doubling the BFC size doesn't just mean adding 25 tons of BFC, but also the needed engines to maintain desired speed, armor/fuel/etc. to match, and so on.
This also becomes less difficult as tech increases. In Steve's BSG AAR, he started with 64k km/4k km/s BFC techs which I would say is an early-to-mid-game tech level, fairly reasonable to achieve before you start mass-producing supercarriers. In this case, the difference between 1x and 2x range is 84% vs 92%, only a +8% difference which is even more of a diminishing return. It does depend a lot on tech level, but I don't think anyone is advocating for beam fighters at very low tech levels, it is clear you do need a minimum tech base for them to be effective (including engine boosting, capacitor and reactor techs, armor, etc.).
Finally, it's important to note that one of the major advantages for beam fighters is flexibility. If you want PD, you will always do better to build large, dedicated PD ships with the best BFCs, AMM systems, etc. Beam fighters are honestly not great for PD, even if you design them purely as PD units they will not be better than a larger ship class, but beam fighters can be a useful augment for your fleet's PD
and an equally capable offensive striking arm in the same package. If we evaluate them solely or even primarily on their PD efficiency, we are missing a large fraction of the point IMO.
also you want to be using the maximum extent of your tracking capability with fighters since thats the advantage fighters have speed, this means if i have a 3000km/s racial tracking i want my fighters going 12kkm/s
This isn't a requirement unless you are trying to compete with a much higher-tech opponent. If you have 3000 km/s racial tracking, but your enemies are flying around with ion engines at ~4500 km/s, you don't need more than 1.5x tracking modifier on your BFCs. In this case maybe you want 2x for future-proofing but there is no
a priori requirement for beam fighters to have the same tracking speed as their flight speed. The exception is if you want to design your beam fighters for PD, but again this is wasteful IMO as dedicating beam fighters to pure PD requires a lot more compromises the make them less flexible and effective in other roles, when larger ships are more effective for PD anyways.
I highly recommend to look closely at the fighter designs in the BSG campaign Steve linked, which show that you can develop very effective beam fighters without having to make them "perfect" with maximum possible speed, range etc. and yet they are still extremely effective.