When I lift I get too tired and fatigued the next day

would it be better if I did moderate weights 8-12 reps

or high weight low reps such as 5x5

bump

shadow box in the gym in between sets like a moron srs

5 sets of bench
5 sets of picking a fight with the biggest guy in the gym
Repeat

srs replies *******s

Less volume.
Drop the intensity a bit. E.g. instead of stopping 1 rep from failure, stop 2 reps from failure.
If you're DLing change to RDLs, squats to bulgarians or something else less fatiguing.

heavy bag work only plus actual sparring.

weights.

This video was done for bjj but the concept will apply the exact same for workloads and goals with boxing. Highly highly reccomend, atleast thumb through some of his points on total work loads and recovery for the week.

When I was doing it, my lifting routine never changed. Mind you, I am doing high reps almost exclusively, 20 rep per set. But I never dropped intensity. At the time, the best course for me was training twice a day, sometimes 3 times a day. Lifting would be in the morning and boxing in the evening. When three times, there would be two lifting sessions and one boxing in the middle of the day. If anything, boxing is way more taxing that lifting, so don't you worry about lifting intensity.

One little trick was a bit of shadow boxing immediately after lifting session, this helped to return the fluid motions.

That was the only way I could get any meaningful progress at both building strength while advancing in boxing technique.

Another trick to advance in both, strength and boxing, is training for a fight. If you are not going for a fight, than train as if you were. Spar at least once a week.

If you are not up to it then just crawl back to your hole, curl up and cry.