SECAM was 625 lines like PAL (about 576 visible). NTSC 525 (about 480 visible)
There were various incompatible Secam systems eventually, surviving till Analogue switch off.
There isn't any necessary connection between NTSC/PAL/SECAM and resolution, the UK experimented with 405-line NTSC, and some S. American countries use 525-line PAL (PAL-M). NTSC just suffered from being first, and by the time other countries moved to colour, the minor shortcomings of NTSC had been noticed and PAL/SECAM invented to fix them. That coincided with 625-lines being the norm.
I don't think the broadcast SECAM signals were ever incompatible at a video level (the French system L used different values for sound/video, but SECAM is SECAM), but there was a strange hybrid for VCR recording called MESECAM (Middle East SECAM). It only ever showed up on VHS systems, AFAIK.
The simpler nature of a SECAM colour signal meant that SECAM-only VCRs could use simple circuitry, PAL was more complex to process. The Middle East was a mix of PAL and SECAM (depended on who the ex-colonial masters were!) so for simplicity they just used PAL-type VCR circuitry everywhere, which was cheaper than a true dual-standard machine. The result was an MESECAM recording that wouldn't play back on a true SECAM VCR.
I remember using an old PAL VCR to record French SECAM TV, it played back fine on a SECAM TV set.