In the English Vocabulary Profile at B1, listed as pronouns:
WHAT = THE THING = used to refer to something without naming it
WHATEVER = anything or everything
However, one of their examples is a cleft for focus:
What I like most about her is her honesty.
is C1 when it is a noun CLAUSE subject.
Similarly, we cover ‘whatever’ in more detail elsewhere.
A search in COCA for verb + what + pronoun + verb:
_V _DDQ _P _V
1 KNOW WHAT YOU’RE 9477 C1 phrase in EVP
I don’t know what you‘re talking about, man.
2 KNOW WHAT I’M 8807
3 KNOW WHAT I MEAN 7839
4 ‘S WHAT I’M 5754 subject complement WHAT NOUN CLAUSE
No, but it‘s what I‘m going to do.
5 KNOW WHAT IT IS 4034
6 ‘S WHAT WE’RE 3292
7 KNOW WHAT IT’S 2839
8 KNOW WHAT THEY’RE 2356
9 ‘S WHAT YOU’RE 2160
10 IS WHAT IT IS 1938
11 ‘S WHAT I WANT 1880
12 KNOW WHAT YOU MEAN 1822
13 KNOW WHAT HE’S 1537
14 ‘S WHAT I WAS 1535
15 ‘S WHAT I DO 1529
16 SEE WHAT I CAN 1468
I’ll see = C1 make a decision about something later
WHAT object noun clause
I‘ll see what I can do for you.
17 KNOW WHAT I WAS 1450
18 ‘S WHAT I THOUGHT 1439
19 KNOW WHAT IT WAS 1434
20 IS WHAT I ‘M 1423
21 ‘S WHAT YOU WANT 1402
22 ‘S WHAT IT ‘S 1365
23 KNOW WHAT YOU ARE 1365
24 KNOW WHAT WE ‘RE 1359
25 DO WHATEVER IT TAKES 1341
I‘m gonna do whatever it takes to get him back.
26 DO WHATEVER YOU WANT 1292
27 DO WHAT YOU WANT 1279
28 KNOW WHAT I THINK 1258
29 KNOW WHAT YOU THINK 1228
30 ‘S WHAT IT IS 1213
31 KNOW WHAT THEY ARE 1213
32 ‘S WHAT I ‘VE 1190
33 ‘S WHAT I THINK 1171
34 KNOW WHAT IT MEANS 1160
35 KNOW WHAT THEY SAY 1158
36 ‘S WHAT YOU DO 1143
37 KNEW WHAT HE WAS 1138
38 ‘S WHAT THEY ‘RE 1132
39 ‘S WHAT HE SAID 1117
40 KNOW WHAT YOU WANT 1108
41 SEE WHAT I MEAN 1097
42 IS WHAT WE ‘RE 1080
43 ‘S WHAT WE DO 1061
44 KNOW WHAT I WANT 985
45 ‘S WHAT I SAID 953
46 KNOW WHAT HE WAS 918
47 IS WHAT YOU ‘RE 915
48 KNOWS WHAT HE ‘S 881
49 SEE WHAT I ‘M 881
50 UNDERSTAND WHAT YOU ‘RE 873
51 UNDERSTAND WHAT I ‘M 855
52 ‘S WHAT HE ‘S 837
53 DO WHAT I CAN 820
54 SEE WHAT YOU ‘RE 771
55 GET WHAT YOU WANT 760
56 ‘S WHAT I DID 748
57 KNEW WHAT THEY WERE 722
58 DO WHAT THEY WANT 720
59 HAVE WHAT IT TAKES 708
60 SEE WHAT WE CAN 707
61 IS WHAT I DO 702
62 KNOW WHAT SHE ‘S 702
63 DO WHAT I WANT 694
64 KNOW WHAT I ‘D 689
65 ‘S WHAT WE ‘VE 682
66 DO WHAT I DO 682
67 GET WHAT THEY WANT 680
68 ‘S WHAT IT WAS 672
69 IS WHAT IT ‘S 659
70 IS WHAT I WANT 650
71 KNOW WHAT THEY WERE 632
72 DO WHAT THEY DO 628
73 KNEW WHAT IT WAS 627
74 IS WHAT YOU GET 623
75 DO WHAT YOU HAVE 622
76 KNOW WHAT YOU DID 608
77 ‘S WHAT I LIKE 605
78 KNOW WHAT I DID 604
79 KNEW WHAT I WAS 601
80 ‘S WHAT I WANTED 600
81 ‘S WHAT YOU NEED 598
82 ‘S WHAT I CALL 590
83 ‘S WHAT THEY DO 586
84 DO WHATEVER THEY WANT 583
85 KNOW WHAT I WOULD 582
86 DO WHAT YOU CAN 580
87 IS WHAT WE ARE 580
88 ‘S WHAT I MEAN 576
89 DO WHAT YOU DO 568
90 SEE WHAT YOU CAN 565
91 ‘S WHAT WE HAVE 558
92 DO WHAT WE CAN 552
93 IS WHAT YOU WANT 538
94 ‘S WHAT SHE SAID 537
95 ‘S WHAT WE NEED 535
96 IS WHAT YOU DO 528
97 KNOW WHAT I AM 527
98 SAY WHAT YOU WANT 525
99 IS WHAT WE HAVE 524
100 ‘S WHAT YOU GET 521