If you're going to do this, use some but not all of your cash from your reserve and get the rest from liquidating the majority of your brokerage account.
You don't mention what your cost basis is in the brokerage account, but even if it's 2/3rds gains and only 1/3 cost basis and you need $120k after using $30k of cash, we're still talking only $12k in capital gains taxes, not a life changing amount of money.
Pulling contributions out of your Roth account gives up that potential for long term tax free growth forever. A 401k loan just puts extra financial pressure on you after you've bought the house and can lead to sticky situations if (for example) you lose your job, triggering a need to repay the loan right away or have it recharacterized as a distribution with associated income tax consequences.
Now in your shoes I wouldn't be buying million dollar home that is half again my entire net worth. I particularly would be buying a million dollar home that was half again my entire net work as an investment property. But you didn't as my/our opinion on whether not not it was a good thing to do, just the least bad way to to go about doing this thing.