Is it better to sell, pay off mortgage and capital gains and take the cash to invest in another property or is it better to refi/ETO and take the cash to invest in another property?

This may seem counterintuitive but, they are an "insider" to that group and gain a bit of empathy-points.

Once you start to get people in there to look at project to project, that will give you a baseline then you'll start to gain more knowledge on where you need to be on the pricing/estimates etc.

Notice when I spoke of London STR I used the words "gain control of a property" and NOT "buy a property"???? 

No but keep track of those repairs as it will add to your cost basis when you go to sell it and have to pay capital gains.

Thus, my main goal joining this forum is to try to gain confidence in the decision to get into real estate investment and better understand the risks that I may not be considering due to my lack of experience in the field.

A lot of the US market - housing, stock, treasuries, etc - is basically a legal money-laundering location for honest or ill-gotten gains in the rest of the world, because the markets are open to foreigners and as close to a guaranteed safe haven as can be found.

However, after accounting for long-term capital gains tax and other expenses, you would be left with $150k which is important to budget and account for.

Investing close to home allows you to gain hands-on experience, learn the ropes, and be more involved in the day-to-day.

@Tori Rhodes faster ways to scale:Buy a portfolio from another investor- Get seller financing from a savvy one that doesn't want capital gains hit!