is fighting inside the best tactic when fighting a tall fighter with long reaches?

It depends on who youre fighting. If they're slow n uncoordinated you can out box them like haye did against Valuev. The overhand right is your best friend against a taller opponent. But to answer your question it's probably best to stay on the inside. The first 20 secs should be the feeling out stage where u access how you're going to beat him. Look to see if he's fast, repetitive or anything like that, then do what u have to do. Boxing is a game of chess. Try to get the better of your opponent mentally n I assure you, you'll win.

That depends if he is better at grappling then you,

You also need to be able to read what kind of fighter he is, you can tell a lot by there body movements,

Ever person is diffrent, I know some large people then have no power for striking when in close, others have a lot

Or is this under rules

Ima just give u examples of effective shorter that are great at fighting short fighters so u check them out and figure it out

Joe Frazier, Bob and weave mid-ranger

Mike Tyson, excellent at slipping punches with great headmovement

Aaron Pryor, unorthadox, his foot speed helped alot

Roman Gonzalez, cuts off the ring like no other fighter, also slips punches as he comes forward and uses short combos against taller fighters

Regilio Tuur, great at using jabs to the body to close the distance, lands his combos and gets out of range so his opponents dont pick their spots

Odlanier Solis, unorthadox, he pressures to force his opponent to throw punches and counters those punches. A rare pressure counterpuncher.

sidenote, their are shorter fighters that dont fight short like Rigondeax, u cant study those type of guys cause they have a very complex approach