Two moh questions!

I have two MOHs too and they didn’t really know each other but they have gotten to know one another better since. I started a group chat with all my girls, which led them to start their own private group chat away from me for planning purposes. As far as “duties” it’s really up to them what they choose do. When I asked them I explained to each of them that they can decide amongst themselves who does what if they are planning any events, and that either or both of them are welcome to do a speech if they wish. I’m sure you chose them because they are great friends and great friends will try and make you feel special during this time and hopefully work well together to do this. I wouldn’t add extra stress to your plate by trying to assign things, just make sure they have each other’s contacts and let them do their thing !

Maybe start a convo between the both of them in the same chat, just talk about your ideas and wants, and let them kind of figure it out and plan on their own. I wouldn't "define" certain tasks or events for them just because one may be better financially and the other may be better time wise, so leave it up for them to discuss and decide. I am sure together they can plan on contribute the same amount on both.

Eventually I am sure there will be a group chat started with you MOH and bridesmaids, and they will all want to help and contribute in their own ways!

There's no defined rule for the MOH. Technically they're just titles and however involved you want them to be in up to you. They also don't have to be evenly split, especially if your MOH's don't mind. Based on what I read here, some people get really offended if there's even a slight hint of difference in "seniority/hierarchy" or amount of work to do but you seem to think they get along and won't be a problem.

Are you planning to have any event other than the bachelorette party, like a shower? If so, you can give each MOH one event each. Bachelorette party can be planned by MOH in the states since it's not hometown based (unless you want to stay put in London) and bridal shower by the childhood friend MOH since it'll be a local event. If you don't plan to have a bridal shower, maybe the rehearsal dinner?