Bot's not up to date. Tsk tsk
Inferior product, incorrect, IB and IG have different purposes but you need to know the difference between things like investing and speculating and trading, or short and medium and long duration positions, or probability and return expectation, to be able to understand which one suits which purpose, I know simply by a few snippets of information, you will have to go through a multi month to year learning curve, sometimes you need both types, actually three types but you haven't got that far yet, which is what we did when I was managing a 50% per quarter family office.
Mr. 50% per quarter.
How does one get exposure on brokers deal with this? As in, how do I know how brokers actually implement this behind the scenes? How they actually segregate funds?segregation of funds to limit contagion from trading mistakes.
What is a 50% per quarter ?
Are you implying you were doing close to 500% per year with compounding?

How does one get exposure on brokers deal with this? As in, how do I know how brokers actually implement this behind the scenes? How they actually segregate funds?
Is there a way to know beyond the "ye ye our funds are segregated and secure bla bla" found on T&Cs?
Commission: IB 0.005 or below IG 0.02, so 4 times higher .Good isn't it, anyway there you have your answers from other people above, I have more experience, used more brokers including all mentioned, in all scenarios from retail to institutional, using all account sizes, with all asset classes.
-IG for CFDs which have leverage advantages
-"If you prioritize low commissions and a comprehensive trading platform, Interactive Brokers"
Nothing in life comes for free, what no one has mentioned is the margin issue with IB, firstly they are higher than other brokers with leveraged positions while usually providing lower leverage, however the issue is their 'variable' margin where at times if you trade too close to the edge, which you will never know is the edge being a 200% uplift of original margin, you will be liquidated, with Stocks this issue is negated.
The interesting part of this is that no one provided any detail whatsoever, choosing a broker is an intensely complex 3D spreadsheet with variables such as AUM, trading style, asset class, long or short focus, leverage used, trade size to deposited capital, hold duration of trades and investments, timeframes in focus, and probably the most important - segregation of funds to limit contagion from trading mistakes.
Not the brokers segregating funds, you segregating funds to stop contagion of your capital (time), the world is intensely lazy, they're not going to do it for you and will happily enable your contagion (money).
https://www.elitetrader.com/et/threads/a-theory-about-good-vs-bad-traders.373180/page-4#post-5781053
What are you smoking?