"I have anxiety issues. Is a sustained dosage of CBD tincture more effective at controlling my anxiety, or should I just take it when I feel more anxiety?"
I would go with a sustained dose of CBD while tirtrating (increasing or decreasing) until optimal effect is achieved, especially if your anxiety is severe or on a daily basis.
There is good clinical evidence of CBD being helpful in reducing anxiety, but not much regarding the issue of taking it all the time versus just when calming is needed. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4604171/ In view of CBD’s lack of toxicity there is no practical reason not to give it a try and keep some kind of diary to see if over a few weeks time if it has been helpful.