Presumably, a Bitcoin spot ETF won't be paper bitcoin because they'd have to hold actual bitcoin, with a predetermined ratio of shares to bitcoin.

A Bitcoin futures ETF is totally paper bitcoin. But we already have bitcoin futures ETFs.

IMO, it will be harder to manipulate the price of bitcoin with futures contracts than it is for precious metals, because it's much much easier for people to trade the primary market directly and actually make and take delivery of the underlying commodity.