Any stock/bond buying through a broker is always on street name. One is segregated (ie when no margin loan ) and the other is rehypothated in the market (when there is margin loan) ie IBKR does not use its own money to fund the margin loan.
My understanding is that a cash account is not in street name.
a margin account is and the firm can lend the stock out (largely to shortsellers) regardless if you have a margin debit. If they do, you do not get the dividend but rather a payment in leiu. The only economic different is the tax treatment. A dividend can be qualified for long term tax treatment, a payment in leiu is treated as ordinary income.