Taking control of the dynamic bitcoind tx fee I'm running bitcoind for a service that works with quite small user withdraws most of the time.
Recently I noticed that instead of the standard 0.0001 tx fee from the recent past, it already charges up to 0.0008 for some transactions which I find expensive for this specific use case. (I read about that update to dynamic fees but then forgot about it)

getinfo gives "paytxfee" : 0.00000000" by the way.
I haven't explicitly set the fee in bitcoin.conf

So, if one doesn't want to take advantage of the dynamic fee but set a fixed one 
- How is best to do it? Just "bitcoin-cli settxfee 0.0001" or in the .conf file? Would it actually be enforced or it will still disregard it in some cases?
- if it actually works to set it as fixed, how do you think that would affect the confirmation time? Will 0.0001 be fairly enough for the time being to get in the very next block?
First: remind settxfee is not a absolute fee per transaction. It's a fee per kilobyte.

Example:


Alice sends 1BTC to Bob
Alice has 11 times 0.1 BTC in her wallet (she received 11 times 0.1 BTC from different persons)
Alice transaction will require all 11 x 0.1BTC inputs to create the 1BTC-to-Bob-transaction
Therefore the transaction is bigger (in terms of bytesize) then if she would hold 1 x 1.1BTC in her wallet.


Bitcoin-Core will only accept transaction to it's mempool which contains the minimum fee.