PhD student and slow, painstaking writer. Any advice? I am a PhD student (in the UK, and part-time, member of faculty at the same time)
But I struggle to write well and fast. To quote my supervisor:
The greatest weakness [of your report] is a ground hog day feel to it. I feel like you've woken up and started your narrative afresh at various places (this may be the reality) but a more consistent effort could improve efficiency of expression and clarity.
If effort alone solved this, I wouldn't be asking this question, but this does point to a long-standing problem. I am a slow, painstaking writer, with a history of overcoming impairment / clumsy pen-holding. Even in my native language (French) and in any topic.
My usual &quot;strategy&quot; has been to accept that limit and work with it, by:

Focusing on science (computing was transformational for me at school, thanks to typing and programming Maths/Science homework)
Displacing writing with work that provides material - preparing diagrams, software, bibliographies, synthetic tables, that can make their way in the work
&quot;pre-writing&quot; - like a procrastinator using pre-commitment, writing for a conference paper because the short term and specific focus kick-starts a short document
&quot;recycling&quot; writing. Starting again appears to fail, so I rework existing wording and presentations, e.g. merging an earlier report with a conference paper and new material; torturing sentences to adapt them to a new order...
Building a top-down structure first, and focusing on structure - to avoid the patchwork quilt impression that re-using written material would leave.
I have tried recording myself, as my speech can be clearer, but this has proved very inefficient too - suddenly a lot of umming and erring; speaking above family is also not always an option.

But (as well as still being a lot of work) this results in the poor efficiency of expression and lack of clarity that my supervisor remarks. At worst, the work can be a collection of tables, diagrams, bibliographic notes, commented to give them context. Hopefully it is not always as bad, but:

What other strategies would you recommend?
My &quot;paradigm&quot; has been to accept, my limited writing. What practices would help me change paradigm? If am not limited to my history, what would I do to level up?
This is not a complete answer as it is only one possible strategy, but it became too long for a comment.
My advice would be to read lots, and not just academic papers and textbooks. Read well-written fiction, in English preferably, since that is the language you have to write in at the moment. I personally like the Sherlock Holmes stories as they are short and fun, though the language is a little archaic due to the time period they were written in. Otherwise just browse the fiction section of your local bookshop (or online equivalent) until you find something that catches your attention.
When reading, think about how the author varies their language and sentence structure according to the effect they want to create (short, sharp sentences to show surprise or anger, for example). Try to notice how they build the narrative, and how they structure the story. However, don't do this for every single book you read as that would quickly get tiring. Prioritise reading enjoyable books and over time you will hopefully get a feel for how to construct pleasing sentences and sustain longer passages of writing.
It could also be that your technique of amalgamating past work leads to your &quot;ground hog day&quot; style. Out of all the possible strategies you list, I think that creating a structure and sticking to it will be the best for helping you to avoid this problem. Let me use my thesis writing strategy as an example:

I made a list of all the chapters I would include and a one sentence description of the material that would go in each chapter.
For each chapter, I made a bullet point list of all the topics that would be covered in that chapter.
For each topic, yet another list or short description of the key points I needed to cover.

Overall, I ended up with something like this:
Chapter 1 (background cosmology)

introduction

historical overview
topics covered in this chapter


general relativity

field equations
FLRW solution
figure showing spacetime shapes


dark energy models

LCDM
quintessence
k-essence



Chapter 2 (methodology)
etc ...
This structure leaves me with an almost paragraph-by-paragraph plan of what to write. Then it's just a case of filling in the blanks, i.e. writing a paragraph or two for each of those items on the list. Adding material such as tables and figures comes last, though their rough placement does appear in the list. The additional benefit of this is that you can show your plan to your supervisor even before you finish writing, and they can suggest things that you missed or topics you could skip.
Finally, your comment about clumsy pen-holding made me wonder if you have considered the possibility that you could be dyslexic? There are many strategies to help with that which I won't go into here; a quick google search should help you. If you think that could be part of the problem, your university may have an office specifically for supporting students and staff with dyslexia (and other related difficulties) and I recommend you get in touch with them for some one-on-one advice.