Even Cassette Basic offered many features not present in the 6502 dialects, including the ability to use long variable names, support for both single and double-precision floating point, support for both 16-bit and 32-bit integer types, support for hex and octal numbers, and many other features.
[Maury Markowitz' answer already nails it, so this is just to add some numbers for comparison]
The Cassette BASIC 1.0/1.1 in the IBM PC ROM is a Microsoft BASIC V5.x (*1). It's usually marketed as MBASIC. It was available as stand alone application or as program under CP/M and other OS. MS offered 3 basic flavours:
8 KiB BASIC
The early versions of Microsoft BASIC required 4KB of ROM
The 4k versions lacked a number of major features, including string variables. These were added in the 8k versions. The equivalent 6502 version, which also expanded the floating point from 32 to 40 bits, was about 10k.
But Microsoft's IBM BASIC (known as "Cassette BASIC") for the original
IBM PC ...
"C.ADJ" represents "Color Adjust" - the 14.318MHz signal is used to derive the NTSC clock for the CGA card, so adjusting the trimmer affects the colours that appear if the composite output jack is in use.
AFAIK there is just one 14.318MHz crystal (not an oscillator) on the 5150 motherboard, right next to the 8284. It’s a flat metal component with two leads coming out of it from one side, probably marked with 14.318MHz. There might be a solid wire soldered to its housing, going across it. I’m pretty sure it was labeled as Y1 on the PCB.