I'm relatively new to Monero, but am extremely interested in it since it seems to be the best privacy coin out there. When opening Monero-Gui for instance, why are there multiple options for blockchain referencing? What are the downsides of Bootstrapping? Are there some docs that give more of an intuition behind all of the security options? I'm assuming there is a good security reason behind downloading the entire ~150 GB blockchain just to use XMR.
There are three modes available in the GUI, namely
Simple mode (bootstrap) and
Simple modemode, the GUI wallet will automatically connect to a remote node and have a simple interface. This mode excludes the need for the blockchain sync and ensures you can immediately use the wallet. However, it weakens your privacy insofar as the remote node will be able to see your IP address as well as associate any of your transactions with your IP address. Besides, using a remote node does not contribute to the strength and decentralization of the network.
Simple mode(bootstrap) mode, the wallet automatically connects to a remote node whilst syncing your own (local) node in the background. The wallet will subsequently switch to your own (local) node once it is fully synced. This allows you to immediately use the wallet while still eventually using your own (local) node (which is optimal for privacy and contributes to the strength and decentralization of the network). Additionally, this mode has a simple interface as well. This mode is the default and is thus recommended by the developers for new users.
Advancedmode, you will perform the blockchain sync from scratch (which may take from 10-14 hours (with an SSD) to several days to complete (with an HDD) and requires approximately 120 GB of free disk space) without connecting to a remote node. Advanced mode also contains all features that were deemed as advanced by the developers (and thus were left out of the simple mode). Note that you won't be able to properly use your wallet until the blockchain sync from scratch has been completed. Lastly, Advanced mode allows you to customly set a remote node (in case you, for instance, want to connect to your own remote node).
P.S. Extensive documentation for the GUI can be found here: