If you are tuned with a 150 grain head, can you take a100 grain head and a 50 grain incert, and make it shoot the same or will it change things due to the fact the incert is further up in the shaft
Same outcome. To minimal for a trad guy to notice.
You won't notice the change, and I doubt it would even show up with shots out of a shooting machine.
However, If you use a 50 gr brass insert in place of a 20 gr stock aluminum insert -- then things are not the same when you make the switch.
Thus:
A 150 gr head with a 20 gr aluminum insert = 170 gr
A 100 gr head with a 50 gr brass insert = 150 gr
Just be sure to account for all of your components.