I do not recommend any mods until...
Gun fit has been done, correct basic fundamentals learned, lessons from a pattern board, and lot and lots of rounds fired starting with light targets loads have been fired.
Once all this done, make arrangements to take a defensive shotgun class with that bone stock shotgun that fits you, and is becoming an extension of you.
Arrive at this class with a willing attitude , notebook, and pen.
The instructor will understand you have a gun, gun fitted to you , you know 4 rules of safety, and really have put in the time and effort and range time to get to know this gun.
Instructor will ask about YOUR defensive situation, and from assessment, be able to recommend for YOU , YOUR environment, what would work best for as for as any mods, if any at all.
If...If any mods are suggested, instructor will make recommendations as to specific items that work.
One big thing is, often time measurements are tweaked even more, and suggestions of getting a second gun, with these measurements are made and any mods that might be suggested be done with the second gun.
The first gun you have [taking a class with] is now not only a backup, also one for general use, like hunting, clay games...etc.
Aside-
Many folks here set up the home gun, as per instructors suggestion, for the smaller person in the house, like the wife.
Bigger person can shoot a smaller gun - a smaller person cannot always effectively use a bigger gun.
Like the LOP (length of pull) being too long.
Oh, FWIW, the best kept secret is a bone stock semi auto 20 ga shotgun.
Like an 1100, Beretta 303, 390, Win 1400...
Deal is, these owners have lots of trigger time, and lots of hours of mindset.