Hi.
Something that I recommend that you could mention on your personal statement would be studying the reliability of historical sources. For example, this could include literature, other forms of art, letters, speeches, diaries, ect.
I'm going to apply to uni for English and History next year, so I've done a good bit of research into what to put in a personal statement.
The reliability of sources is something that I've not seen anyone do in history personal statements that I've read online, but I think that it could definitely work really well. You could even make it more niche and look into the reliability of sources during a certain time period (e.g., Russia/the USSR in the 19th and 20th centuries), or how the reliability of certain sources has improved or lessened over time.
A useful website that I've used to look at personal statements is Anyverse. It's allowed me to see what sort of time periods and issues are commonly mentioned, as well as how I should speak about what I've learnt in my personal statement. It's also helped me understand what I've already done and what I can do to build on it between now and next summer.
I hope this helps, and if you have any more questions, feel free to ask me. 😊