Yes, kratom could be immensely helpful even though methadone is one of the worst opiates to withdraw from and that's a super high dose. I prefer red-vein strains, as they're best for pain relief, relaxation & have the most typical opioid effects. White veins are the most stimulating and greens are in the middle in terms of sedation/stimulation. Yellow and Gold strains are variations of white and red-vein varieties that have been dried differently. Many people like to make "blends" with several different strains, myself included.
Some popular strains are:
White Horn Kali
Green Ketapang
Red Hulu Kapuas
Yellow Vietnam
Bentuangie
White Maeng Da
Green Elephant
Red Bali
(Don't get too hung up on strain names. Focus more on finding a reliable vendor with quality product instead).
Most new users start at 1-2 grams of kratom powder and work their way up. It can cause vomiting and "wobbles" if you take too much, so it's better to start with a low dose until you know how it affects you. Some people prefer brewing it into tea while others do a simple "toss 'n wash" with the dry powder. And some prefer using capsules to get it down. It's not going to give you a buzz with that tolerance, so set your expectations low and you'll be pleasantly surprised.
If I were you, I'd taper to a lower dose of methadone before quitting and switching entirely to kratom (assuming that's your plan). If not, you should definitely be able to reduce your dose of methadone with the help of kratom. Just don't combine them, as they act on the same on the same receptors to an extent.