How do you use LLC properly? Business credit for Series LLC?

[Kevin Jung]

I apologize in advance for the lengthy post. 

A little background: I own 2 rental properties in TX. Both are under my name, and not in an LLC. (I don't plan on getting them under an LLC right now.) Anyways, I created my first LLC in TX (member-managed) last month after finding out about the business credit side. I got my EIN, Duns, business checking/savings account, and just got approved for a 10K business credit card.

Q1: Can I use this LLC & its bank accts to manage both of my rental properties' income and expense; **even though they are not under an LLC? I will keep good books to separate the two or hire a bookkeeper.

Q2: I plan on investing in TX primarily, but I'm in MS temporarily and want to buy a property in MS soon. What are the details for setting up LLC in MS? I figure set one up as a member-managed, foreign LLC tied to my TX LLC? Do I get a new EIN/Duns # again? Doesn't that create a whole new business credit score?

Q3: But I also want to get a Series LLC in TX (I screwed up.. should have created one in the first place). Should I just use my new TX LLC to manage the 2 rental properties I have and create a completely new Series LLC?

Or should I convert it to series LLC? If so, how does converting LLC to series LLC work since I have bank accounts, EIN, and Duns #? Do you update all of them to the new series LLC name? Does my business credit score follow along?

Will it have issues with having MS LLC tied to it? I read that series LLC should keep in-state properties only. And MS also doesn't recognize Series LLC.

Q4: In the future, once I get the Series LLC, I read I could have a different EIN for each children series. But wouldn't that create a whole new business credit score for them? Do you have to file separate taxes for each children series that have an EIN?

Q5: I watched a bunch of Clint Coons's youtube videos and he mentioned that you should create a management LLC to manage all the income/expenses for all the children series LLCs. That's my primary goal and I don't really care about anonymity such as setting up one in Wyoming, Nevada, and etc. But Question is, is that management LLC part of the series LLC or a separate LLC?

Thanks so much for taking your time to read all.