I believed the microarchitecture used in a MIPS microprocessor, is the pipeline one, but I might be wrong?
Thanks in advance for your answers!
MIPS is an ISA; you can implement it however you like. Some hobby projects implement it in a non-pipelined way, but the ISA was designed around a https://en.wikipedia.org/wiki/Classic_RISC_pipeline - in fact being easy to pipeline was the whole point of RISC, and of the Stanford MIPS project. (Commercial MIPS evolved out of that research project.)
The first commercial MIPS, R2000 was a 5-stage RISC which implemented the MIPS I ISA, was designed so that one branch delay slot was sufficient to hide branch latency.
But MIPS R10000 was a 4-wide superscalar out-of-order design with register renaming.
Other later MIPS implementations are embedded CPUs with shorter pipelines, and once again in-order execution. https://en.wikipedia.org/wiki/MIPS_architecture#Uses