The Hannah pen is fairly accurate, it correlated closely with a brand new single junction probe I put on my controller, I calibrated them at the same time using the same reference solutions (4 and 7). Dip type devices like the Hannah pen really need calibrated every time you remove it from its storage solution and go to use it (for accuracy). When using it to perform a profile you’ll want to keep the probe in the tank the entire time and switch it on to take measurements (it’ll auto power down after a few minutes).
Using a pH meter (or controller) with a BNC connected probe for long period immersion measurement is the easiest, as long as it is calibrated. Single junction probes will wear out and be harder to calibrate for accuracy over time so if you want the highest accuracy and longevity you will need a Double Junction probe, unfortunately finding one at sub £100 prices is not common, Apex Neptune comes to mind.
The more accuracy you want and better ease of use won’t be in the cheap bracket unfortunately.
As long as you don’t mind slight/extreme drifting inaccuracy over long term submersion measurements then single junction probes would suffice on a meter/controller, enough to perform months of accurate profiles at least. If you need monitoring or controlling accurately long term then using double junction probes will give you better mileage.
I wouldn’t trust the accuracy of my eyes performing profile changes in 0.1 pH increments and testing using colorimetry either with liquid indicators or paper indicators. Good for top and bottom of profiles though, also good for determining the atmospheric equilibrium CO2 pH if you shake the beejeezus out a liquid colorimetric test or let a paper test stabilise in colour (colour changes as CO2 coms out of solution).