Quick test: Make two identical arrows, one with your current 150 grain head and another with 190 grain head of your chioce. Take several careful, intentional shots with each arrow. Be really sure to use the same grip, anchor point and aim. If both arrows hit the same spot you are good to go.
If your arrows are a bit weak spine, or even spot on correct spine for the 150 grain heads they will probably impact to the right with 190 grain. (Excessively stiff shafts will impact left of point of aim, weak shafts impact to the right). Target tip arrows will probably impact the same spot - broadheads WILL be more sensitive.
Depending on how much extra length you have past the riser at full draw you can stiffen the current shaft by cutting it shorter. (Shorter shaft is stiffer than the same shaft in longer length).