Bismuth can be configured using config.txt file. To keep your custom configuration intact, you can also create config_custom.txt, copy the original settings there and adjust them. Individual lines are explained below:

Port on which server part of the node is running. As of now, it is not recommended to change this value.
Genesis address. This value should not be changed.
Blockchain signature verification. When set to 1, every transaction signature in the blockchain will be verified.
Version of the protocol, if it does not match configuration of other nodes, you will not be able to connect to the network.
Limit of number of outgoing client threads to be created. Once this limit is reached, node will not accept more incoming connections or attempt to create outgoing connections.
Change this value to the IP of the pool in case you are mining with the default miner for a pool. For solo mining, this part can be ignored.
Change to 1 to perform database maintenance on startup to save some drive space.
If configured to 1, you will receive more precise debug messages in the output window. Development feature.
Can be adjusted to INFO in case you want to see what is going on in the background. Development feature.
When set to 1, deletes all nodes from the peerlist to which node cannot connect on startup.
Pause between checks for new blocks in seconds. You can increase this value to lower processor usage or lower it to get block updates faster (useful when mining)
Number of mining threads for the default miner.
Number of cycles the default miner runs before asking node for a new difficulty.
Path to the ledger. It is recommended to keep this value intact as it is not yet cross-compatible.
When set to 1, ledger will compress on each startup, pruning transactions without “keep=1”, saving space and increasing operational speed. History older than 10,000 blocks will be lost.
Number of warnings issued to other nodes for misbehavior before banning them.
Set to 1 if you want to be running node through a Tor proxy
Default miner will wait until ledger is synced before it starts mining if set to 1. Setting this to 0 can get you banned by other nodes.
List of whitelisted nodes for more computationally demanding tasks and direct block submission. Leave “any” in if you want to accept from all nodes.
Set to 1 if you want to be using a mining pool with the default miner.
Address of the pool if you are mining for it.
Enable usage of random access memory instead of using drive all the time. Requires memory proportional to the current blockchain size, tolerates hyperblocks.
If you are running a default pool, this is the difficulty percentage for accepting shares as compared to the real difficulty.
You can change this IP if you are using a remote node.