Planning to start new SIP

Hi. I have invested 2,00,000 in SBI Long term equity fund back in 2022. Started SIPing 10k in Nippon small cap in Nov 2023. Planning to add a mid cap fund in my portfolio & invest 5k more. Will that be a good approach? If yes, then which mutual fund? Considering long term horizon of 15+ years. Risk appetite is high.