Bitcoin is not a PoS and so you cannot stake it as if it's part of its system or blockchain. The staking feature that's being told by these platforms and exchanges are wanting to deposit our BTCs on them and they will earn through lending it and they'll give a portion of that interest to us as our profits. I wouldn't 'stake' my Bitcoin to any of them, as you've said if it's another strategy that you trust, I'd rather hold it on my wallet and wait for the price to increase. Because that's safer and I hold my BTCs and can sell anytime I want to and even if you'd say that it's on a flexible term, you'll never know what might happen to the platform where you have deposited or staked it.