Qualcomm Quick Charge (QC) is one of the oldest and most widely known protocols; its various versions (QC 2.0, 3.0, 4+, 5) delivered progressively higher power levels and smarter voltage adjustment over time. QC was, for a long stretch, the default fast-charging method on most Android phones.
USB Power Delivery (PD) stands out as an open, brand-independent industry standard; usable by manufacturers beyond Qualcomm, it has become the most widely accepted solution today. Most modern phones, tablets and laptops support PD.
Huawei's SCP (SuperCharge Protocol) was developed to deliver high-power charging on its own phones and generally offers limited compatibility outside its own ecosystem. Similarly, OPPO's VOOC and SuperVOOC are designed for maximum performance on their own phones, but drop to standard PD speed when used with other brands.
Most of these protocols fall back to backward compatibility when plugged into a different device; a PD-certified charger will still work with a VOOC phone, just at PD's standard speed rather than VOOC's full speed. This is exactly what explains why the same phone charges at different speeds with different chargers.
The practical advice for anyone who wants brand-independent flexibility is to choose a PD-certified charger; it offers broad compatibility and consistent performance regardless of phone brand. This is exactly why Charjett's chargers prioritize the PD standard.