This video covers the core I consider to be the best choice for your 100w (any mode) End Fed Half Wave antenna across the entire HF spectrum.

Link to the spreadsheet of my EFHW transformer efficiency comparisons -

https://docs.google.com/spreadsheets/...

Link to core on Digikey -

https://www.digikey.co.uk/en/products...

Link to the core on Mouser -

https://www.mouser.co.uk/ProductDetai...

Link to the myantennas transformer using this core -

https://myantennas.com/wp/product/mef...

Link to Adam K6ARK's antenna kit on Amazon -

https://www.amazon.com/K6ARK-100W-End...