Autumn term Y1 is essentially an extension of EYFS, treat it as such and plan as if it is. You've got EYFS experience - lean on it and use it. Can you use continuous provision if your SLT are reasonable? Don't over plan. Planbee is good for projects.
Phonics - you know how to teach phonics. The schemes are all much of a muchness with a few slight differences so you'll pick it up. The sounds at this point in the year aren't too confusing. Trust yourself.
Speak to the English subject lead and see if they can assist with previous plans or rewriting medium term plans? The Power of Reading by CLPE is good but it isn't a full scheme to follow, cherry pick from it and don't bothered reading the entire scheme plans, they can be repetitive.
Can you buddy up with the Y2 teacher for their support as well, or ask to buddy up with another local school Y1 team/ school in the academy group?
PowerPoints - don't bother unless you have to. And even then keep them minimal. Instead of showing them pictures on a PPT, physically model everything to them. Writing? Do it with a pen on flip chart paper then stick it on the wall - instantly display. Maths - use physical resources, model pictorials on flip chart papers stick it on the wall for instant display after. Go old skool - maybe that's why there aren't PPTs from last year!?
Worksheets? Use Twinkl and don't reinvent the wheel. Or otherwise keep them basic, aim for group tasks. My worksheets are often just the date and LO with a single picture, printed 6 times so one for each group and I'll scribe for them.
You're on supply which gives you the beauty of being able to walk away if it's too much. It really isn't worth battering yourself over. Your mental health is worth more.
Aim for "good enough".