how long does it take to download all the blocks for full node?
and how safe is qt wallet full node compared to the ledger?
Assuming that you have a fiber connection or medium-speed internet, you need an average of 2 to 5 days to complete the synchronization. The faster the internet and the better the specifications of your device, the shorter the period.
But why do you need to run a full node?
Hardware wallets provide you higher security, while full nodes such as bitcoin cores give you greater privacy, so it is better to buy a hardware wallet instead of running a bitcoin core ( if you are planning for security, not privacy.) ledger are a bad choice for hardware wallets and you should avoid them.
The current blockchain size is around 550 MB and the time it takes to download that depend on your internet speed
GB*