I'm of a similar view to Mick - I keep a 'day-book' rather than formal diary, as sometimes I need more than a page and some days I don't! If the proverbial should hit the round spinning thing then it is what a court would regard as 'contemperaneous notes' which can be helpful (don't ask!). This is complimented by a smartphone which can be used to take photos and dictation for lengthy comments etc, plus an ipad on which we keep all our generic and dynamic RAs and technical manuals as a point of reference. As a lot of my work is near water then I often use the ipad to take backup photos, although the use of cloud storage is making that redundant these days.
I think the key part of your enquiry is your final sentence where you say you are not really tech minded but have a hunch that if it were set up correctly it would help streamline things. For it to help effectively then I think you might be better to try and identify what processes you actually want to streamline, how they link together, and what software/apps might help with this. For example, can quotes be prepared using a pro-forma - if so then that is simple to set up on an ipad or similar, incorporating photos etc to avoid ambiguity. I do the same with inspection reports that I prepare. However, linking it all to a central 'hub' - be it a PC, server or cloud storage, will require careful thought and is not as intuitive as some make out!
In early December I called in at an Apple store whilst visiting the big smoke, and asked for some help with my new (to me) phone. Long story short - they offer free workshops on all of their devices which can be tailored to your specific needs. Within a fortnight I had attended a total of three workshops - two on macbooks and one on the phone. The most popular seem to be the ones relating to ipads. I think the workshops are 'on hold' for a couple of weeks whilst they deal with the new year sales etc, but will be restarting later this month.
A further thought is with regard to compatibility. If you have an iphone then an ipad makes sense - the ipad should be capable of running most office software and will link easily with the phone. The big advantage of Apple products is the ease with which they link together. However, if that isn't the case then an Android tablet, or even a chromebook, might be more helpful. I used to write source code for mainframes in a fomer life and have worked with PCs for more than 35 years (and still do), but it has taken a lot of effort to be able to work efficiently with both PC and Apple devices.