There is no site as you can not avoid conflicts with grade 5 engineering on hardpoints weapons...
People are just remembering that if the blueprint is NOT grade 5. you are likely at the Wrong engineer so don't pin it and yes there will be a better engineer as all items can be done to grade 5 at a engineer in the bubble... No items are grade 3 or grade 4 max only, they all can be done to grade 5... many are only done at grade 5 at one single engineer...
Inara engineering page is complicated... but when listing a modification that you want it does state which engineer will be grade 5 and which is not and in many cases there is only one single engineer for grade 5...
Start with blue prints
The community site for Elite: Dangerous, Starfield with the game databases, information, gaming news and other handy content...
inara.cz
and then select the item you want in the section you want and the modification on that item, scroll down to grade 5 and it lists the engineer that you will need to pin..
You will have no choice when it come to conflicting items like beam lasers Vs burst for grade 5 of each by design you can only have 1 of them as the same engineer does both to grade 5...
so you can only have 1 blueprint pinned...
You just go through core items in your ship and look for grade 5 in the bubble listed on site..
Frameshift drive grade 5 - Elvira Martuuk no choice - as the others require high explorer rank
Power Distributor - Charge enhanced (Grade 5)
The Dweller - no choice only grade 5 option..
Thrusters - Dirty (Grade 5) - Professor Palin - no choice only grade 5 option (pain in the back side to unlock)
Power Plant - Overcharged (Grade 5) - Hera Tani - no choice only grade 5 option...
junk like sensors can be done at multi engineers... do last..
Optional internals
Shield Generator - Thermal resistant (Grade 5) - Lei Cheung - no choice only grade 5 option...
Hull Reinforcement Package - Heavy duty (Grade 5) - Selene Jean - no choice only grade 5 option, this will conflict with Armour and is unavoidable you can only pin 1 grade 5 pick one, once complete, do the other.
With hardpoint/weapons,
By design fdev made a single grade 5 engineer the only single engineer to do grade 5 lasers at all for all the laser types in Broo Tarquin - again hes the only choice for grade 5 lasers... no body else... pick one type
Go though all the other weapon types you want to..
PAs - Bill turner.. no choice
Multi cannon or rail guns grade 5, both require the same engineer for grade 5 you can not pick both only 1 - Tod "The Blaster" McQuinn only grade 5 option for both weapons..
frag cannons - Zacariah Nemo no choice that only grade 5...
All this is listed on Inara for bubble engineering...